Color filter, coloring composition for color filter and liquid crystal display device

ABSTRACT

A coloring composition for a color filter, which includes a transparent resin, an organic pigment dispersed in the transparent resin, and a retardation-regulating agent containing a compound which is capable of increasing a retardation. A color filter which is provided with colored pixels formed on a transparent substrate by using this coloring composition. A liquid crystal display device which is provided with this color filter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2007-021897, filed Jan. 31, 2007,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a coloring composition for creating a colorfilter, enabling the perpendicular (thickness-wise) optical retardationof each of color pixels to be adjusted to become optimal, a color filterwherein the perpendicular optical retardation of each of color pixels isoptimized, and a liquid crystal display device which is provided withsuch a color filter.

2. Description of the Related Art

A liquid crystal display device is a display device wherein thebirefringence of liquid crystal molecules is utilized and which isconstituted by a liquid crystal cell, a polarizing element and anoptical compensating layer. This liquid crystal display device isroughly classified, depending on the kind of light source, into atransmissive type liquid crystal display device, in which the lightsource is installed inside the device, and a reflection type liquidcrystal display device, in which an external light source is utilized.

The transmissive type liquid crystal display device is constructed suchthat two polarizing elements are mounted on the opposite sides of theliquid crystal cell, and one or two optical compensating layers areinterposed between the liquid crystal cell and the polarizing element.

On the other hand, the reflection type liquid crystal display device isconstructed such that a reflective plate, a liquid crystal cell, anoptical compensation layer and a polarizing element layer aresuccessively arrayed in the mentioned order. The liquid crystal cell isconstructed such that orientated bar-like liquid crystalline moleculesare sandwiched between two substrates and that as a voltage is appliedto electrode layer(s) which is (are) disposed on the opposite sides orone side of the substrates, and the aligned state of bar-like liquidcrystalline molecules is caused to change, thereby making it possible toperform the switching of the transmission/shielding of light.

Depending on the alignment of the bar-like liquid crystalline molecules,the liquid crystal cell is permitted to take various display modes, suchas TN (Twisted Nematic), IPS (In-Plane Switching), FLC (FerroelectricLiquid Crystal), OCB (Optically Compensated Bend), STN (Supper TwistedNematic), VA (Vertically Aligned), and HAN (Hybrid Aligned Nematic).

The polarizing element is generally constructed such that a transparentprotective film made of triacetyl cellulose (herein referred to as TAC)is attached to the opposite sides of a polarizing film formed of anoriented polyvinyl alcohol (herein referred to as PVA) in which iodineis diffused.

As for the optical compensating layer, there have been proposed variouskinds of layers. For example, in the case of a VA (Vertically Aligned)mode liquid crystal display device which is capable of performing ahigh-contrast display, there has been employed an optical retardationfilm exhibiting negative birefringence anisotropy, with the optical axisthereof being perpendicular to the substrate thereof (or negative Cplate) together with an optical retardation film exhibiting positivebirefringence anisotropy with the optical axis thereof being horizontalto the substrate thereof (or positive A plate) (for example, see JP-A2000-136253 (KOKAI)).

In recent years, because of the thinness in wall thickness and theresultant advantages such as space-saving, lightweight properties,power-saving, etc., liquid crystal display devices are now rapidlypropagated, especially as a display device for televisions, and,consequently, it is required to further enhance various displayperformance factors, such as the brightness, contrast andomnidirectional visibility.

More specifically, a liquid crystal display device such as an IPS or VAof a normally black mode which makes it possible to realize furtherenhanced contrast and a wider view field display is employed asespecially preferable for use in televisions. With respect to theaforementioned optical compensating layer, many are designed to obtainan optimal value so as to make it possible to minimize the generation ofcoloring on the occasion of viewing a black color from the front of thetelevision and to minimize the color shift on the occasion of viewingthe television obliquely.

There is, however, a problem that, when the values of perpendicularoptical retardation of red colored display pixels, green colored displaypixels and blue colored display pixels constituting the color filter(hereinafter, referred to as Rth(R), Rth(G) and Rth(B), respectively)differ from each other, coloring is caused to generate on the occasionof viewing a black color obliquely.

Especially, when the values of perpendicular optical retardation of redcolored display pixels, green colored display pixels and blue coloreddisplay pixels constituting the color filter are non-uniform, i.e.Rth(R)<Rth(G)>Rth(B) or Rth(R)>Rth(G)<Rth(B), it is no longer possible,for the optical compensating layer which is designed to exhibitunidirectional (continuous) wavelength dispersion to the wavelength oflight, to compensate the non-uniform values of perpendicular opticalretardation among these colors at such a high level in display qualitythat is demanded nowadays.

More specifically, even though it is possible to realize excellentvisibility as the display face is observed from the front side thereof(the direction perpendicular to the display face), when the display faceis observed obliquely at an angle of 45 degrees (hereinafter, referredto simply as oblique visibility), only the light of a specific color iscaused to leak, resulting in coloring of black color to generate areddish, bluish or greenish black color.

Since the magnitude of retardation of a color filter is relatively smallas compared with that of other components to be employed in a liquidcrystal display device, the aforementioned problem was not consideredseriously up to date. However, in the case of the liquid crystaltelevision where high contrast and wide viewing-angle properties aredemanded, the aforementioned problem cannot be disregarded any longer.

Especially, in the case of the liquid crystal television where a highcontrast of not less than 1000 or not less than 3000 is demanded, sincethe quality of the black color image is required to be excellent, theaforementioned problem cannot be disregarded any longer.

Since the optical designing is now generally performed centering aroundthe green color, if the magnitude of retardation of green display pixelsdiffers greatly from that of red and blue display pixels, light leakageis caused to generate, thus raising problems with respect to the obliquevisibility of the display device. With a view to overcome this problem,there has been proposed to incorporate a macromolecule having a planarstructure group on its side chain into a colored macromolecular membraneor to incorporate birefringence-reducing particles having abirefringence index which is opposite in sign (positive or negative) tothe macromolecule into a colored macromolecular membrane, thereby tryingto reduce the magnitude of retardation which the color filter has (forexample, see JP-A 2000-136253 (KOKAI) and JP-A 2000-187114 (KOKAI)).

As a matter of fact however, it has been discovered as a result ofstudies made by the present inventors on this problem, that the value ofperpendicular optical retardation of the color filter differs greatlyaccording to the kind of pigment to be employed, the fineness anddispersed state of the pigment, or the kind of matrix resin (forexample, acrylic resin or cardo resin). Therefore, it has been foundimpossible to expect sufficient effects even with the aforementionedmethods of incorporating a macromolecule having a planar structure groupon its side chain or birefringence-reducing particles into a coloredmacromolecular membrane, thus failing to solve the aforementionedproblem.

Especially, in the case of a color filter wherein a transparent resin,represented by acrylic resin, which enables organic pigments to bereadily dispersed therein, is used as a substrate for a high-contrastliquid crystal display device, it has been found difficult to improvethe oblique visibility while securing a desired high-contrast value (notless than 1000, more preferably not less than 3000).

Additionally, according to the prior art, it was simplisticallybelieved, erroneously, that an excellent color filter is one with asmaller birefringence, and even though many studies have been made onthe means for improving the oblique visibility, no serious study hasbeen made on the means for minimizing the difference in values ofperpendicular optical retardation to such a level that does not raiseany problem as a high-contrast liquid crystal display device to therebyregulate the perpendicular optical retardation of each color to anoptimal value.

Meanwhile, it has been discovered by the present inventors that theretardation of the color filter layer of each of red, green and bluepixel patterns differs depending on the color, i.e. red is enabled toindicate positive or negative retardation, blue is enabled to indicatepositive retardation and green is enabled to indicate negativeretardation.

BRIEF SUMMARY OF THE INVENTION

A first object of the present invention is to provide, for the purposeof enhancing the oblique visibility in a high-contrast liquid crystaldisplay device based on the aforementioned novel findings, aphotosensitive coloring composition which makes it possible to suitablycontrol the values of perpendicular optical retardation of the red,green and blue color pixels constituting a color filter.

A second object of the present invention is to provide, through acombination of an optical compensation layer with other constituentmembers based on the aforementioned novel findings, a liquid crystaldisplay device which is capable of preventing the generation ofundesirable coloring as the display face is observed not only from theaxial direction (or normal direction) of the display face but also fromthe direction biased from the axial direction by an angle of 45 degrees,and also capable of securing excellent front visibility (normaldirection to the display face); or to provide a color filter wherein thevalue of perpendicular optical retardation is suitably controlled so asto secure the aforementioned features.

A third object of the present invention is to provide a liquid crystaldisplay device which is capable of preventing the generation ofundesirable coloring even if the display face is observed obliquely, andis hence excellent in visibility, and which can be manufactured througha combination of the aforementioned color filters with an opticalcompensation layer and other constituent members.

According to a first aspect of the present invention, there is provideda coloring composition for a color filter, which comprises a transparentresin, an organic pigment dispersed in the transparent resin, and aretardation-regulating agent containing a compound which is capable ofincreasing a retardation.

According to a second aspect of the present invention, there is provideda color filter comprising a transparent substrate, and colored pixels ofat least one color which is formed on the transparent substrate, whereinthe colored pixels are formed using a coloring composition including atransparent resin, an organic pigment dispersed in the transparentresin, and a retardation-regulating agent containing a compound which iscapable of increasing a retardation.

According to a third aspect of the present invention, there is provideda liquid crystal display device comprising: a first transparentsubstrate having a thin film transistor array and a first transparentelectrode formed thereon; a second transparent substrate disposed toface the first transparent substrate and having a color filter and asecond transparent electrode formed thereon; and a liquid crystal layerinterposed between the first transparent substrate and the secondtransparent substrate; wherein the color filter is provided with coloredpixels of at least one color which are formed on the second transparentsubstrate by using a coloring composition including a transparent resin,an organic pigment dispersed in the transparent resin, and aretardation-regulating agent containing a compound which is capable ofincreasing a retardation.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a cross-sectional view schematically illustrating the colorfilter according to one embodiment of the present invention; and

FIG. 2 is a cross-sectional view schematically illustrating one exampleof a liquid crystal display device which is provided with a color filterof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Next, various embodiments of the present invention will be explained.

The value of perpendicular optical retardation of each of colored pixelsof the color filter according to one embodiment of the present inventioncan be obtained by a method wherein a continuous light containing awavelength of a peak region of visible transmissive light (for example,the wavelength of light ranging from 380 nm to 780 nm) is irradiated ona color filter which is provided with colored pixels of at least threecolors including red 3 (R), green 3 (G) and blue 3 (B) from a locationin front of the color filter and from a plurality of locations which areangled to the surface of the color filter, and the three-dimensionalrefractive index of the light emitted therefrom is measured by makinguse of a retardation-measuring apparatus such as an ellipsometer.

For example, a light having a wavelength of 610 nm in the case of a redcolored pixel, 550 nm in the case of a green colored pixel, and 450 nmin the case of a blue colored pixel is irradiated to the color filterfrom a location in front of the color filter and from at least two otherlocations at an incident angle of 45 degrees to thereby perform themeasurement of optical retardation to obtain three-dimensionalrefractive indexes of Nx, Ny and Nz. Thereafter, the values ofperpendicular optical retardation (Rth) are calculated according to thefollowing formula.

Rth={(Nx+Ny)/2−Nz}×d

Wherein Nx is a refractive index in the x-direction in plane of thecolored pixel; Ny is a refractive index in the y-direction in plane ofthe colored pixel; Nz is a refractive index in the thicknesswise-direction of the colored pixel; Nx being defined as a retardedphase axis represented by Nx≧Ny; and d is a thickness (nm) of coloredpixel.

In this case, if the object to be measured is a color filter, the valueof optical retardation of a single-colored pixel can be determined byperforming the measurement of optical retardation by irradiating lightthrough a mask which is worked to permit the light to pass through onlysingle-colored pixels of R, G or B.

For example, when a light having a wavelength of 610 nm is used as anincident light, it is possible to obtain a value of optical retardationwhich originates only from a red colored pixel; when a light having awavelength of 550 nm is used as an incident light, it is possible toobtain a value of optical retardation which originates only from a greencolored pixel; and when a light having a wavelength of 450 nm is used asan incident light, it is possible to obtain a value of opticalretardation which originates only from a blue colored pixel, thus makingit possible to estimate an approximate value of optical retardation ofsingle-colored pixel of each color.

Incidentally, in the case where the object to be measured is asingle-colored pixel of R, G or B (a coloring composition of a singlecolor is coated on the surface of a transparent substrate), themeasurement of optical retardation can be performed withoutnecessitating any mask.

The coloring composition for a color filter for forming a color filteraccording to one embodiment of the present invention is formed of acoating liquid comprising a base material consisting of a monomer or apolymer such as acrylic resin and cardo resin, which is useful in easilysecuring a high contrast, at least one kind of material selected from anorganic solvent, a photo-polymerization initiator and a curing agent,and an organic pigment dispersed in the base material.

The color filter according to one embodiment of the present inventioncan be obtained by a method in which the aforementioned coloringcomposition is used as a color resist and patterned by means ofphotolithography or by a method in which the aforementioned coloringcomposition is used as an ink and coated by means of an inkjet orprinting.

As for the details of the components constituting the coloringcomposition to be employed for creating the color filter, they will beexplained hereinafter.

The retardation-regulating agent to be employed in the color filteraccording to one embodiment of the present invention is an additivewhich is designed to regulate the perpendicular optical retardation ofthe color filter which is formed as a colored coated film on the surfaceof a transparent substrate, of a reflective substrate or of asemiconductor substrate by making use of the coloring composition forthe color filter.

Especially, the retardation-regulating agent is designed to beincorporated in the coloring composition for a color filter of at leastone kind of color for the purpose of improving the oblique visibility.

In order to secure a high contrast of not less than 1000 or not lessthan 3000, the compound to be used as the retardation-regulating agentis preferably selected from those which are excellent in dispersibility.

More specifically, although it is possible to employ particulatematerials such as inorganic particles as a retardation-regulating agent,it is preferable to refrain from using them due to the opticalscattering and depolarization thereof.

Further, when the colored pixels of plural colors are formed, as a colorfilter, on the surface of a transparent substrate, although it ispossible to incorporate the retardation-regulating agent into all of thecolored pixels of plural colors, the addition of aretardation-regulating agent may be limited to only the colored pixelsof one or two colors.

As for the retardation-regulating agent to be employed in the colorfilter according to one embodiment of the present invention, it ispossible to employ organic compounds which are capable of regulating theretardation so as to increase it.

More specifically, it is possible to employ an organic compound havingone or more planar structure groups having a cross-linking group. Forexample, it is possible to employ, as such an organic compound, at leastone kind of compound selected from the group consisting of melaminecompounds, porphyrin compounds, epoxy compounds and polymeric liquidcrystal compounds.

It is generally considered that it is possible to remove theperpendicular optical retardation of the film as a whole by simplyadding, to the coloring composition, particles having a planar structuregroup and exhibiting a birefringence index which is opposite in sign(positive or negative) to the pigment, or other kinds of resin.

However, when particles having a planar structure group are simply addedto the coloring composition, the particles themselves are caused toorientate at random, thereby reducing the effects thereof to remove theperpendicular optical retardation of the film as a whole.

Under the circumstances, it has been discovered, as a result of profoundstudies made by the present inventors, that when the organic compound isprovided with a planar structure having at least one cross-linkinggroup, the perpendicular optical retardation of the film as a whole canbe greatly changed, thus enabling the organic compound to exhibitsufficient effects.

For example, when the retardation-regulating agent is provided with afunctional group which is capable of cross-linking during thephoto-curing process or thermosetting process in the step ofphotolithography, the planar structure group is prevented from rotatingfreely and is more inclined to orientate in one direction, as a whole,on the occasion of shrinking in the step of thermal setting and thenfixed thereto, thus enabling the retardation-regulating agent toeffectively exhibit the function thereof to control the opticalretardation.

As for specific examples of the planar structure, they include a grouphaving at least one aromatic ring. For example, in the case ofmonocyclic hydrocarbon, it is possible to employ a phenyl group, cumenylgroup, mesityl group, tolyl group, xylyl group, benzyl group, phenethylgroup, styryl group, cinnamyl group, trityl group, etc. In the case ofpolycyclic hydrocarbon, it is possible to employ a pentalenyl group,indenyl group, naphthyl group, viphenylene group, acenaphthylene group,fluorene group, phenanthryl group, anthracene group, triphenylene group,pyrene group, naphthacene group, pentaphene group, pentacene group,tetraphenylene group, trinaphthylene group, etc. In the case of aheteromonocyclic compound, it is possible to employ pyrrolyl group,imidazolyl group, pyrazolyl group, pyridyl group, pyrazinyl group,triazine group, etc. In the case of a heteropolycyclic compound, it ispossible to employ indolydinyl group, isoindolyl group, indolyl group,purinyl group, quinolyl group, isoquinolyl group, phthalazinyl group,naphthylydinyl group, quinoxalynyl group, cinolynyl group, carbazolylgroup, carbolynyl group, acrydinyl group, porphyrin group, etc. Thesegroups may contain a substituent group such as a hydrocarbon group,halogen, etc.

As for the at least one cross-linking group to be attached to the planarstructure group, unsaturated polymeric groups (A, B, C, D, E, F) orfunctional groups (I, J, K, L, M, N, O) or thermally polymerizablegroups (G, H, P, Q, R, S, T, U) can be preferably employed. Among them,epoxy groups (G, H) are more preferable and groups of P—U are mostpreferable for use.

Further, as for the unsaturated polymeric group, it is more preferableto employ ethylenic unsaturated polymeric groups (A, B, C, D).Alternatively, groups such as —CH₂NHCOCH═CH₂,—CH₂NHCO(CH₂)₇═CH(CH₂)₇CH₃, and —OCO(C₆H₄)O(CH₂)₆CH═CH₂ can be alsosuitably employed.

When at least one reactive functional group such as a hydroxyl group isincluded in the planar structure group, these cross-linking groups canbe easily obtained through the reaction between the aforementionedreactive functional group and a compound having a functional group whichis capable of reacting with the aforementioned reactive functional groupand also having an ethylenic unsaturated group such asglycidyl(metha)acrylate, 2-(metha)acryloyloxyisocyanate,tolylene-2,4-diisocyanate, etc.

As for the melamine compound, compounds represented by the followinggeneral formula (1) and available in the market can be preferablyemployed. Alternatively, any kind of compound having any of theaforementioned planar structure groups can be also employed. Followingare examples of melamine compounds.

Wherein R₁, R₂ and R₃ are individually a hydrogen atom, methylol group,alkoxymethyl group or alkoxy n-butyl group; and R₄, R₅ and R₆ areindividually a methylol group, alkoxymethyl group or alkoxy n-butylgroup. It is possible to employ a copolymer having a combination of twoor more kinds of repeated units. Two or more kinds of homopolymers orcopolymers may be co-used.

In addition to the compounds described above, it is also possible toemploy a compound having 1,3,5-triazine ring such as those set forth inJP-A 2001-166144 (KOKAI). Further, the compounds represented by thefollowing general formula (2) can be also preferably employed.

Wherein R₇ through R₁₄ are individually a hydrogen atom, alkyl group,aryl group or heterocyclic group. Among them, the hydrogen atom isespecially preferable.

Further, compounds having a porphyrin skeleton and represented by thefollowing general formula (3) can be preferably employed. In thisgeneral formula (3), n is an integer of 1-20, an integer of 2 being morepreferable.

Wherein R₁₅ through R₂₂ are individually a hydrogen atom, halogen atom,alkoxy group, alkylthio group, substituted or unsubstituted phenoxygroup, substituted or unsubstituted naphthoxy group, substituted orunsubstituted phenylthio group, or substituted or unsubstitutednaphthylthio group.

Following are specific examples of porphyrin compound represented by thegeneral formula (3). As for the halogen atom in R₁₅ through R₂₂, it ispossible to employ fluorine, chlorine, bromine and iodine atoms.Further, as for the alkoxy group and thioalkyl group, although there isnot any particular limitation, it is preferable to employ those whosealkyl group in the substituent group is formed of a linear, branched orcyclic alkyl group having 1-12 carbon atoms. Among them, it is mostpreferable to employ a linear, branched or cyclic alkyl group having 1-8carbon atoms.

X represents hydrogen atom, halogen atom, alkoxy group, substituted orunsubstituted phenyl group, and substituted or unsubstituted phenoxygroup. As for specific examples of the halogen atom, they includefluorine, chlorine, bromine and iodine atoms. As for specific examplesof the alkoxy group, they include a linear, branched or cyclic alkylgroup having 1-12 carbon atoms. Among them, it is most preferable toemploy a linear, branched or cyclic alkyl group having 1-8 carbon atoms.As for specific examples of the substituted or unsubstituted phenylgroup, they include a phenyl group, p-chlolophenyl group, p-bromophenylgroup, and p-nitrophenyl group. As for specific examples of thesubstituted or unsubstituted phenoxy group, they include a phenoxygroup, p-chlolophenoxy group, p-bromophenoxy group, and p-nitrophenoxygroup. Z represents —CH₂— or —N—.

As for specific examples of alkyl group in the alkoxy group andthioalkyl group, they include methyl, ethyl, n-propyl, iso-propyl,n-butyl, iso-butyl, sec-butyl, t-butyl, n-pentyl, iso-pentyl,2-methylbutyl, 1-methylbutyl, neo-pentyl, 1,2-dimethylpropyl,1,1-dimethylpropyl, cyclopentyl, n-hexyl, 4-methylpentyl,3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 3,3-dimethylbutyl,2,3-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl,1,2-dimethylbutyl, 1,1-dimethylbutyl, 3-ethylbutyl, 2-ethylbutyl,1-ethylbutyl, 1,1,2-trimethylbutyl, 1,2,2-trimethylbutyl,1-ethyl-2-methylpropyl, cyclohexyl, n-heptyl, 2-methylhexyl,3-methylhexyl, 4-methylhexyl, 5-methylhexyl, 2,4-dimethylpentyl,n-octyl, 2-ethylhexyl, 2.5-dimethylhexyl, 2,5,5-trimethylpentyl,2,4-dimethylhexyl, 2,2,4-trimethylpentyl, n-octyl, 3,5,5-trimethylhexyl,n-nonyl, n-decyl, 4-ethyloctyl, 4-ethyl-4,5-dimethylhexyl, n-undecyl,n-dodecyl, 1,3,5,7-tetraethyloctyl, 4-butyloctyl, 6,6-diethyloctyl,n-tridecyl, 6-methyl-4-butyloctyl, n-tetradecyl, n-pentadecyl,3,5-dimethylheptyl, 2,6-dimethylheptyl, 2,4-dimethylheptyl,2,2,5,5-tetramethylhexyl, 1-cyclopentyl-2,2-dimethylpropyl,1-cyclohexyl-2,2-dimethylpropyl, etc.

As for specific examples of the substituted or unsubstituted phenoxygroup, they include phenoxy, 2-methylphenoxy, 3-methylphenoxy,4-methylphenoxy, 2-ethylphenoxy, 3-ethylphenoxy, 4-ethylphenoxy,2,4-dimethylphenoxy, 3,4-dimethylphenoxy, 4-t-butylphenoxy,4-aminophenoxy, 4-dimethylaminophenoxy, 4-diethylaminophenoxy, etc.

As for specific examples of the substituted or unsubstituted naphthoxygroup, they include 1-naphthoxy, 2-naphthoxy, nitronaphthoxy,cyanonaphthoxy, hydroxynaphthoxy, methylnaphthoxy,trifluoromethylnaphthoxy, etc.

As for specific examples of the substituted or unsubstituted phenylthiogroup, they include phenylthio, 2-methylphenylthio, 3-methylphenylthio,4-methylphenylthio, 2-ethylphenylthio, 3-ethylphenylthio,4-ethylphenylthio, 2,4-dimethylphenylthio, 3,4-dimethylphenylthio,4-t-butylphenylthio, 4-aminophenylthio, 4-dimethylaminophenylthio,4-diethylaminophenylthio, etc.

As for specific examples of the substituted or unsubstitutednaphthylthio group, they include 1-naphthylthio, 2-naphthylthio,nitronaphthylthio, cyanonaphthylthio, hydroxynaphthylthio,methylnaphthylthio, trifluoromethylnaphthylthio, etc.

As for specific examples of the epoxy compound having a planar structuregroup, they include bisphenol type epoxy compounds such as, for example,bisphenol A epoxy compound, bisphenol F epoxy compound, bisphenol ADepoxy compound, hydrogenated bisphenol A epoxy compound, etc.; novolactype epoxy compounds such as, for example, phenolnovolac epoxy compound,cresolnovolac epoxy compound, etc.; glycidylamine type epoxy compoundssuch as, for example, tetraglycidyldiaminodiphenylmethane,triglycidyl-p-aminophenol, triglycidyl-m-aminophenol,tetraglycidyl-m-xylene diamine, etc.; glycidylester type epoxy compoundssuch as, for example, diglycidylphthalate, diglycidylhexahydrophthalate,diglycidyltetrahydrophthalate, etc.; and heterocyclic epoxy compoundssuch as, for example, triglycidylisocyanurate, etc.

The following chemical formula (4) shows one example thereof.

As for the polymeric liquid crystal compound, although it is possible toemploy a bar-like liquid crystal molecule and a discotheque liquidcrystal molecule, it is especially preferable to employ the discothequeliquid crystal molecule. As for the bar-like liquid crystal molecule, itis possible to employ the liquid crystal molecules described in JP-A2006-16599 (KOKAI). It is also possible to employ other kinds ofbar-like liquid crystal molecules, examples of which includingazomethine compounds, azoxy compounds, cyanobiphenyls, cyanophenylesters, benzoic esters, phenylcyclohexane carboxylates,cyanophenylcyclohexanes, cyano-substituted phenyl pyrimidine,alkoxy-substituted phenyl pyrimidine, phenyldioxanes, tolanes,alkenylcyclohexyl benzonitriles, etc. As for the discotheque liquidcrystal molecule, the molecules described in JP-A 8-27284 (KOKAI) can beemployed. Following are examples of the discotheque liquid crystalmolecule.

In the aforementioned chemical formulas, Y is a bivalent linking groupselected from the group consisting of an alkylene group, alkenylenegroup, arylene group, —CO—, —NH—, —O—, —S— and a combination of any ofthese groups. It is most preferable to employ a group consisting of acombination of at least two kinds of these bivalent linking groups.

As for the number of carbon atoms in the alkylene group, it shouldpreferably be limited to the range of 1-12. As for the number of carbonatoms in the alkenylene group, it should preferably be limited to therange of 2-12. As for the number of carbon atoms in the arylene group,it should preferably be limited to the range of 6-10.

An alkylene group, alkenylene group, or arylene group may contain asubstituent group (for example, an alkyl group, halogen atoms, cyanogroup, alkoxy group, acyloxy group).

R represents at least one kind of cross-linking group selected fromunsaturated polymeric groups (A, B, C, D, E, F) or functional groups (I,J, K, L, M, N, O) or thermally polymerizable groups (G, H, P, Q, R, S,T, U), an alkyl group which is substituted by any of these cross-linkinggroups, an alkenyl group which is substituted by any of thesecross-linking groups, aryl group which is substituted by any of thesecross-linking groups, or a heterocyclic group which is substituted byany of these cross-linking groups. It is also possible to suitablyemploy groups such as —CH₂NHCOCH═CH₂, —CH₂NHCO(CH₂)₇═CH(CH₂)₇CH₃, and—OCO(C₆H₄)O(CH₂)₆CH═CH₂.

Next, there will be explained the color filter according to oneembodiment of the present invention.

As shown in FIG. 1, the color filter according to one embodiment of thepresent invention comprises a glass substrate 1, on which a black matrix2 acting as a light-shielding layer, and colored pixels consisting of atleast three kinds of color, i.e. a red colored pixel 3 (R), a greencolored pixel 3 (G) and a blue colored pixel 3 (B), are disposed.

Incidentally, in addition to these three kinds of color, a complementarycolor may be combined therewith. Alternatively, it is also possible toemploy a color filter of multiple colors, comprising not less than threecolors including a complementary color and any additional color.

Generally, the absolute value of the birefringence index of a colorfilter should be confined to not larger than 0.01. In other words, theperpendicular optical retardation (Rth) should desirably be as close toRth(R)=Rth(G)=Rth(B)=0 as possible.

However, it has been discovered, as a result of profound studies made bythe present inventors, that when the birefringence index of a colorfilter is considered in combination with other constituent members, suchas the wavelength dispersibility of optical retardation, the optimalvalue of perpendicular optical retardation for a color filter existsunder certain conditions other than the situation whereRth(R)=Rth(G)=Rth(B)=0.

The determination of which value is most desirable for the opticalretardation Rth of each of colored pixels in the color filter may differdepending on the combination thereof with other constituent members.What is important is the fact that “in the situation where the Rth ofblue pixel is smaller than that of green pixel, even though the Rth ofgreen pixel is larger than that of red pixel”, or “in the situationwhere the Rth of blue pixel is larger than that of green pixel, eventhough the Rth of green pixel is smaller than that of red pixel”, it isimpossible to realize excellent oblique visibility.

The reason for this can be attributed to the fact that, in the case ofconstituent members represented by an optical retardation plate to beemployed in a liquid crystal display device, the wavelengthdispersibility of birefringence varies unidirectionally (continuously)relative to the wavelength of transmitting light. Therefore, it isnecessary to select a combination which enables to obtain optimumoblique visibility from the combinations of optical members of theliquid crystal display device, such as the liquid crystal, thepolarizing plate, the optical retardation plate and the alignment film.

For the manufacture of the red colored pixel, it is possible to employred pigments such as C.I. Pigment Red 7, 14, 41, 48:2, 48:3, 48:4, 81:1,81:2, 81:3, 81:4, 146, 168, 177, 178, 184, 185, 187, 200, 202, 208, 210,246, 254, 255, 264, 270, 272, 279, etc. Incidentally, this red colorpigment may be employed together with a yellow pigment or an orangepigment.

As for yellow pigments, it is possible to employ C.I. Pigment Yellow 1,2, 3, 4, 5, 6, 10, 12, 14, 15, 16, 17, 18, 24, 31, 32, 34, 35, 35:1, 36,36:1, 37, 37:1, 40, 42, 43, 53, 55, 60, 61, 62, 63, 65, 73, 74, 77, 81,83, 93, 94, 95, 97, 98, 100, 101, 104, 106, 108, 109, 110, 113, 114,115, 116, 117, 118, 119, 120, 123, 125, 126, 127, 128, 129, 147, 151,152, 153, 154, 155, 156, 161, 162, 164, 166, 167, 168, 169, 170, 171,172, 173, 174, 175, 176, 177, 179, 180, 181, 182, 187, 188, 193, 194,199, 213, 214, etc.

As for orange pigments, it is possible to employ C.I. Pigment Orange 36,43, 51, 55, 59, 61, 71, 73, etc.

When the red color display pixel contains at least one kind of pigmentselected from diketopyrrolopyrrol-based red pigment andanthraquinone-based red pigment out of the aforementioned pigments, itwould become easy to obtain a desired value for the R_(Rth) and hencethe employment of these red pigments is preferable.

This is because, regarding the pulverizing treatment ofdiketopyrrolopyrrol-based red pigment, the Rth thereof can be madepositive or negative as desired and the absolute value thereof can becontrolled more or less, while in the case of the anthraquinone-basedred pigment, a value of Rth which is close to 0 can be easily obtainedirrespective of the pulverizing treatment thereof.

As regards the hue, lightness, film thickness and pixel contrast, thecomposition of a red colored pixel should preferably be formed of 10-90%by weight of diketopyrrolopyrrol-based red pigment and 50-70% by weightof the anthraquinone-based red pigment both based on a total weight ofthe pigments. When the pixel contrast is taken into account, thecomposition of a red colored display pixel should preferably be formedof 25-75% by weight of diketopyrrolopyrrol-based red pigment and 30-60%by weight of the anthraquinone-based red pigment, both based on a totalweight of the pigments.

For the purpose of regulating the hue of a red colored pixel, the redpixel may contain a yellow pigment or orange pigment. However, inviewpoint of enhancing the contrast, it is more preferable to employazo-metal complex type yellow pigments.

As for the mixing ratio of the azo-metal complex type yellow pigments,it is preferable to confine it to the range of 5-25% by weight based ona total weight of the pigments. If the mixing ratio of the azo-metalcomplex type yellow pigments is less than 5% by weight, it would becomeimpossible to regulate the pixel hue, thus failing to obtainsufficiently increased lightness. If the mixing ratio of the azo-metalcomplex type yellow pigments is larger than 30% by weight, the pixel huemay be excessively shifted to a yellowish color, thus deteriorating thecolor reproducibility.

As for the diketopyrrolopyrrol-based red pigment, it is preferable toemploy C.I. Pigment Red 254, for the anthraquinone-based red pigment, itis preferable to employ C.I. Pigment Red 177, and for the azo-metalcomplex type yellow pigments, it is preferable to employ C.I. PigmentYellow 150, in order to secure excellent light resistance, heatresistance, transparency and tinting strength.

As for the green colored pixel, it is possible to employ green pigmentssuch as C.I. Pigment Green 7, 10, 36, 37, 58 etc. This green colorcomposition may be employed together with a yellow pigment. As for theyellow pigment, it is possible to employ the same kinds of yellowpigments as employed in the aforementioned red colored pixel.

From the viewpoints of the hue, pixel lightness and film thickness, thecomposition of a green colored pixel should preferably be formed of30-90% by weight of a metallophthalocyanine halide-based green pigment,5-60% by weight of an azo-based yellow pigment and 5-60% by weight ofthe quinophthalone-based yellow pigment, all based on a total weight ofthe pigments. It is more preferable to confine the content ofmetallophthalocyanine halide-based green pigment to 50-85% by weight,the content of azo-based yellow pigment to 5-45% by weight, and thecontent of quinophthalone-based yellow pigment to 5-45% by weight, allbased on a total weight of the pigments.

As for the metallophthalocyanine halide-based green pigment, it ispreferable to employ C.I. Pigment Green 7, 36, for the azo-based yellowpigment, it is preferable to employ C.I. Pigment Yellow 150, and for thequinophthalone-based yellow pigment, it is preferable to employ C.I.Pigment Yellow 138, in order to secure excellent light resistance, heatresistance, transparency and tinting strength.

As for the blue colored pixel, it is possible to employ blue pigmentssuch as C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 60,64, etc. Further, these blue pigments may be used together with a violetpigment, specific examples of the violet pigment including C.I. PigmentViolet 1, 19, 23, 27, 29, 30, 32, 37, 40, 42, 50, etc.

When the blue colored display pixel contains at least one kind ofpigment selected from a metallophthalocyanine-based blue pigment anddioxazine-based violet pigment out of the aforementioned pigments, it ispossible to easily obtain a value of Rth which is close to 0.

From the viewpoints of the hue, pixel lightness and pixel filmthickness, the composition of a blue colored pixel should preferably becomposed of 40-100% by weight of a metallophthalocyanine-based bluepigment and 1-50% by weight of the dioxazine-based violet pigment allbased on a total weight of the pigments. More preferably, the bluecolored pixel should contain 50-98% by weight ofmetallophthalocyanine-based blue pigment and 2-25% by weight of thedioxazine-based violet pigment based on a total weight of the pigments.

From the viewpoints of the light resistance, heat resistance,transparence and tinting strength of the pixel, it is preferable toemploy C.I. Pigment Blue 15:6 as the metallophthalocyanine-based bluepigment and C.I. Pigment Violet 23 as the dioxazine-based violetpigment.

As for the inorganic pigment, it is possible to employ a metal oxidepowder, metal sulfide powder, metal powder such as yellow lead, zincchrome, red iron oxide (III), cadmium red, ultramarine blue, Prussianblue, chromium oxide green, cobalt green, etc.

Further, in order to secure excellent coating properties, sensitivity,developing properties while making it possible to retain a balancebetween the chroma and lightness, these inorganic pigments may be usedin combination with organic pigments. For the purpose of toning, each ofthe color display pixels may further contain dyes within the limitswhich do not deteriorate the heat resistance of the pixels.

In order to realize enhanced brightness and enhanced contrast of thecolor filter, the pigments to be contained in each of the colored pixelsshould preferably be selected from those which have undergone apulverization treatment or those whose average primary particle diameterd50 is relatively small.

The primary particle diameter d50 of pigment can be determined using astandard method which includes calculating by taking the picture of thepigment by making use of a transmission electron microscope and directlymeasuring a size of the primary particles by the image analysis of thepicture. More concretely, the primary particle diameter is determined bymeasuring the major axis and minor axis of the primary particles of eachpigment, and averaging these values. The primary particle diameter d50herein represents a particle diameter (a diameter of equivalent circle)which corresponds to a particle diameter as measured where an integratedquantity in the cumulative curve of number particle size distribution is50% of the total quantity. Even if either a transmission electronmicroscope (TEM) or scanning electron microscope (SEM) is employed, thesame results are obtained.

The average primary particle diameter d50 of the pigment shouldpreferably be confined to not larger than 40 nm, more preferably notlarger than 30 nm, most preferably not larger than 20 nm. Further, theaverage primary particle diameter d50 of the pigment should preferablybe not smaller than 5 nm. If the average primary particle diameter d50of the pigment is larger than 40 nm, the visibility of a liquid crystaldisplay device on the occasion of displaying black would bedeteriorated. On the other hand, if the primary particle diameter d50 ofthe pigment is smaller than 5 nm, it may become difficult to realizesatisfactory pigment dispersion, thereby making it difficult to maintainthe stability of the color composition and to secure the fluidity of thecolor composition.

As a result, the luminance and color characteristics of the color filtermay be deteriorated. Especially, the axial or front visibility would bebadly affected by the employment of organic pigments having an averageparticle diameter d50 of larger than 40 nm.

The contrast C (C=Lp/Lc) can be calculated by a method wherein each ofthe colored pixels formed on a transparent substrate is sandwichedbetween a pair of polarizing plates with a backlight applied to one ofthe polarizing plates and emitted from the other of the polarizingplates, and then measuring the luminance of light emitted using aluminance meter. This enables measurement of the luminance of lightunder a condition in which these polarizing plates are disposed parallelwith each other to determine the luminance of light (Lp), and alsomeasurement of the luminance of light under a condition in which thesepolarizing plates are disposed intersected orthogonally with each otherto determine the luminance of light (Lc). Using the above measurements,the ratio between (Lp) and (Lc) is calculated to determine the contrastC (C=Lp/Lc). When the contrast that can be obtained using simply asubstrate having no colored pixel is defined as CS, the ratio between Cand CS should preferably be: C/CS>0.45.

By minimizing the retardation of all the colors and by regulating thisC/CS to C/CS>0.45, it is possible to minimize the coloring of a blackcolor and hence to perform well-balanced black color.

Especially, when the contrast of a red colored pixel is represented byCR, the contrast of a green colored pixel is represented by CG, and thecontrast of a blue colored pixel is represented by CB, as long as CR, CGand CB satisfy the conditions of CR/CS>0.45, CG/CS>0.45 and CB/CS>0.45,it is possible to obtain excellent front visibility on the occasion ofdisplaying a black image on the liquid crystal display device, asindicated in the following Table 6. Namely, it is possible to reproducea crisp black color without accompanying light leakage.

On the other hand, when the conditions of CR/CS>0.45, CG/CS>0.45 andCB/CS>0.45 are not completely satisfied, i.e., CR/CS≦0.45, CG/CS≦0.45 orCB/CS≦0.45, the light leakage would become prominent on the occasion ofdisplaying a black image, thus failing to obtain a liquid crystaldisplay device which is excellent in front visibility.

When the difference in retardation among all the colors is furtherminimized, it is possible to obtain a liquid crystal device which isexcellent in both oblique visibility and front visibility. Incidentally,even if the conditions of CR/CS>0.45, CG/CS>0.45 and CB/CS>0.45 areentirely satisfied, if the difference in retardation among all thecolors is large, the oblique visibility may become insufficient. This isthe case of Comparative Example 6 where a retardation-enhancing agent isnot incorporated into the green pixel, as shown in the following Table8.

As for the means for controlling the average primary particle diameterof pigment and also controlling the perpendicular optical retardation,it is possible to employ a method wherein a pigment is mechanicallypulverized, thereby controlling the diameter and shape of the primaryparticle (so-called attrition method); a method wherein a solution ofpigment dissolved in a good solvent is introduced into a poor solvent,thereby precipitating a pigment having a desired primary particlediameter and a desired particle shape (so-called precipitation method);and a method wherein pigment having a desired primary particle diameterand a desired particle shape is manufactured on the occasion ofsynthesizing the pigment (so-called synthetic precipitation method).Depending on the synthesizing method and chemical characteristics of thepigment to be employed, any suitable method may be optionally selectedfor each pigment.

Following are explanations about the aforementioned methods. As for thespecific method for controlling the primary particle diameter andparticle shape of a pigment to be incorporated into the colored pixelsconstituting the color filter of the present invention, any of theaforementioned methods may be suitably selected.

The attrition method is a method wherein a pigment is mechanicallykneaded together with a grinding agent, such as a water-solubleinorganic salt such as salt, and with a water-soluble organic solventwhich does not dissolve the grinding agent, by making use of a ballmill, a sand mill or a kneader (hereinafter referred to as saltmilling), after which the inorganic salt and the organic solvent areremoved through water washing and dried to obtain a pigment having adesired particle diameter and a desired particle configuration. However,since there is the possibility that crystal growth is caused to occur inthe pigment due to the salt milling treatment, it would be effective toincorporate a solid resin which can be partially dissolved by theaforementioned organic solvent and a pigment-dispersing agent on theoccasion of the salt milling treatment to thereby prevent crystalgrowth.

With respect to the mixing ratio of the pigment and the inorganic salt,when the ratio of the inorganic salt becomes large, the refiningefficiency of the pigment can be enhanced but the throughput of thepigment is caused to decrease, thereby deteriorating the productivity.

Because of this, it is generally preferable to confine the mixing ratioof the inorganic salt to 1-30 parts by weight, more preferably 2-20parts by weight per one part by weight of the pigment. On the otherhand, the water-soluble organic solvent is employed herein so as to makethe pigment and the inorganic salt into a uniform agglomerate, so thatthe water-soluble organic solvent can be employed at a mixing ratio of0.5-30 parts by weight per one part by weight of the pigment, though itmay depend on the mixing ratio between the pigment and the inorganicsalt.

More specifically, the attrition method is performed as follows. Namely,a small amount of a water-soluble organic solvent is added as a wettingagent to a mixture comprising a pigment and a water-soluble inorganicsalt and then vigorously kneaded by making use of a kneader, etc. Theresultant mixture is then introduced into water and stirred by makinguse of a high-speed mixer to obtain a slurry. This slurry is thensubjected to filtration, water washing and drying to obtain a granularpigment having a desired primary particle diameter and configuration.

The precipitating method is a method wherein a pigment is dissolved in asuitable kind of solvent and then mixed with a poor solvent, therebyprecipitating pigments having a desired primary particle diameter and adesired particle configuration. According to this precipitating method,it is possible to control the size of the primary particle diameter andthe particle configuration by suitably selecting the kind and quantityof these solvents, the precipitation temperature, the precipitatingrate, etc.

Since a pigment cannot be easily dissolved in a solvent in general, thesolvents that can be employed are limited. Specific examples of thesolvents that can be employed are strongly acidic solvents such asconcentrated sulfuric acid, polyphosphoric acid, chlorosulfonic acid;and basic solvents such as liquid ammonia, dimethyl formamide solutionof sodium methylate, etc.

As a typical example of this precipitating method, there is known anacid pasting method wherein a pigment is dissolved in an acidic solventto obtain a solution, which is then introduced into another solvent tothereby re-precipitate fine particles, thus obtaining a pigment havingdesired features. In this case, in viewpoint of manufacturing cost, amethod of pouring a sulfuric acid solution into water is generallyemployed in the industry.

Although there are no particular limitations with respect to theconcentration of the sulfuric acid, it is generally preferable toconfine it to the range of 95 to 100% by weight. Although there are noparticular limitations with respect to the mixing ratio of the sulfuricacid and the pigment, if the mixing ratio is too small, the viscosity ofthe resultant solution would become too high, thus making it difficultto easily handle the solution. On the contrary, if the mixing ratio istoo large, the treatment efficiency of the pigment would bedeteriorated. Therefore, the mixing ratio of sulfuric acid to thepigment should preferably be confined to the range of 3-10 times(weight) the weight of the pigment.

Incidentally, the pigment is not necessarily required to be completelydissolved in the solvent. The temperature on the occasion of dissolutionshould preferably be confined to the range of 0-50° C. If thetemperature is lower than 0° C., the sulfuric acid may freeze and,additionally, the solubility of the pigment will be decreased. On theother hand, if the temperature is higher than 50° C., a side reaction ismore likely to occur.

The temperature of the water to be poured should preferably be confinedto the range of 1-60° C. If the temperature of the water is higher than60° C., the water may boil due to the heat of dissolution on theoccasion of pouring water into the sulfuric acid, thus making the workvery dangerous. On the other hand, if the temperature of the water islower than 1° C., the water may freeze. The time for the pouring ofwater should preferably be confined to 0.1 to 30 minutes based on oneweight part of the pigment. If the pouring time is prolonged, theprimary particle diameter tends to become larger.

The control of the primary particle diameter and the particleconfiguration of the pigment may be performed by a combination ofmethods consisting of the precipitating method such as the acid pastingmethod and the attrition method, such as the salt milling method. Thiscombination method is more preferable in the respects that it can beperformed while taking the degree of grinding into consideration andthat the fluidity of the dispersed body can be suitably secured.

In order to prevent flocculation of the pigment in the course ofcontrolling the primary particle diameter and the particle configurationof the pigment during the salt milling or the acid pasting, a dispersingagent such as a pigment derivative, a resin type pigment dispersingagent, or a surfactant as shown below can be additionally employed.Further, when the control of the primary particle diameter and theparticle configuration of pigment is performed in the presence of two ormore kinds of pigments, it would become possible to obtain a stabledispersed body of pigments even if the pigments are inherently difficultto disperse if they are treated individually.

As a specific type of precipitation method, the leuco method is known,in which, when a vat dye type pigment such as a flavanthrone pigment,perinone pigment, perylene pigment, indanthrone pigment, etc. is reducedby making use of alkaline hydrosulfite, the quinine group thereof isturned into a sodium salt of hydroquinone (leuco compound), thus makingit water-soluble. When a suitable oxidizing agent is added to thisaqueous solution to oxidize the pigment, a pigment which is insoluble inwater and small in primary particle diameter can be precipitated.

The synthesizing precipitation method is a method for precipitating apigment having a desired primary particle diameter and a desiredparticle configuration concurrent with the synthesis of the pigment.Since filtration, which is a typical separation method, is difficult toperform unless pigment particles are flocculated into large secondaryparticles on the occasion of taking up the refined pigment products froma solvent, this synthesizing precipitation method is generally appliedto a pigment such as azo type pigments, which can be synthesized in anaqueous system where secondary flocculation can easily take place.

Further, as for the means for controlling the primary particle diameterand the particle configuration of the pigments, it is also possible toemploy a method wherein a pigment is dispersed for a long period of timeby making use of a high-speed sand mill (so-called dry milling methodfor dry-milling a pigment), thereby making it possible to minimize theprimary particle diameter of the pigment concurrently with thedispersion of the pigment.

Following is an explanation with respect to the coloring composition tobe employed for forming each of the colored pixels of a color filteraccording to one embodiment of the present invention.

The pigment carrier to be contained in the color composition to beemployed for forming the color display pixels of a color filter isemployed for dispersing the pigment, and is formed of a transparentresin, precursors thereof or a mixture thereof.

The transparent resin to be employed herein should preferably have apermeability of not less than 80%, more preferably not less than 95% ina total wavelength range of 400-700 nm of visible light.

As for specific examples of the transparent resin, it is possible toemploy a thermoplastic resin, thermosetting resin and photosensitiveresin. The precursor may be a monomer or an oligomer which is capable ofcreating a transparent resin through the curing thereof by theirradiation of radiation. The resins and precursor can be employedsingly or in combination of two or more kinds thereof.

The pigment carrier can be employed at a ratio ranging from 30 to 700parts by weight, more preferably 60 to 450 parts by weight based on 100parts by weight of the pigments in the color composition.

In a case where a mixture consisting of a transparent resin and theprecursor thereof are to be employed as a pigment carrier, thetransparent resin can be employed at a ratio ranging from 20 to 400parts by weight, more preferably 50 to 250 parts by weight based on 100parts by weight of the pigments in the color composition.

Further, the precursor of the transparent resin can be employed at aratio ranging from 10 to 300 parts by weight, more preferably 10 to 200parts by weight based on 100 parts by weight of the pigments in thecolor composition.

As for the thermoplastic resin, it is possible to employ, for example, abutyral resin, styrene-maleic acid copolymer, chlorinated polyethylene,chlorinated polypropylene, polyvinyl chloride, vinyl chloride-vinylacetate copolymer, polyvinyl acetate, polyurethane resin, polyesterresin, acrylic resin, alkyd resin, polystyrene, polyamide resin, rubbertype resin, cyclized rubber-based resin, celluloses, polybutadien,polyethylene, polypropylene, polyimide, etc.

As for the thermosetting resin, it is possible to employ, for example,an epoxy resin, benzoguanamine resin, rosin-modified maleic resin,rosin-modified fumaric acid resin, melamine resin, urea resin, phenolresin, etc.

As for the photosensitive resin, it is possible to employ resins havinga linear macromolecule into which a photo-curable group such as a(metha)acryloyl group, styryl group, etc. has been introduced through areaction between a linear macromolecule having a reactive substituentgroup, such as hydroxyl group, carboxyl group, amino group, etc. and a(metha)acrylic compound having a reactive substituent group such as anisocyanate group, aldehyde group, epoxy group, etc. or cinnamic acid.

It is also possible to employ a linear macromolecule containing an acidanhydride, such as a styrene-maleic anhydride copolymer orα-olefin-maleic anhydride copolymer half-esterified with a(metha)acrylic compound having an hydroxyl group, such ashydroxyalkyl(metha)acrylate.

As for specific examples of the monomers and oligomers which are theprecursors of the transparent resin, they include various kinds ofacrylic esters and methacrylic esters such as2-hydroxyethyl(metha)acrylate, 2-hydroxypropyl(metha)acrylate,cyclohexyl(metha)acrylate, polyethyleneglycol di(metha)acrylate,pentaerythritol tri(metha)acrylate, trimethylolpropane(metha)acrylate,dipentaerythritol hexa(metha)acrylate, tricyclodecanyl(metha)acrylate,melamine(metha)acrylate, epoxy(metha)acrylate, etc.; (metha)acrylicacid; styrene; vinyl acetate; (metha)acryl amide;N-hydroxymethyl(metha)acryl amide; acrylonitrile; etc. These compoundscan be employed either singly or as a mixture of two or more kindsthereof.

If the color composition is desired to be cured through the irradiationof ultraviolet rays, a photo-polymerization initiator may be added tothe color composition.

As for specific examples of the photo-polymerization initiator useful inthis case, they include an acetophenone-based photo-polymerizationinitiator such as 4-phenoxy dichloroacetophenone,4-t-butyl-dichloroacetophenone, diethoxyacetophenone,1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one,1-hydroxycyclohexylphenyl ketone,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one,2-benzyl-2-diamino-1-(4-morpholinophenyl)-butan-1-one; a benzoin-basedphoto-polymerization initiator such as benzoin, benzoin methyl ether,benzoin ethyl ether, benzoin isopropyl ether, benzyldimethyl ketal,etc.; a benzophenone-based photo-polymerization initiator such asbenzophenone, benzoylbenzoic acid, benzoylmethyl benzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone,4-benzoyl-4′-methyldiphenyl sulfide, etc.; a thioxanthone-basedphoto-polymerization initiator such as thioxanthone,2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone,2,4-diisopropylthioxanthone, etc.; a triazine-based photo-polymerizationinitiator such as 2,4,6-trichloro-s-triazine,2-phenyl-4,6-bis(trichloromethyl)-s-triazine,2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine,2-piperonyl-4,6-bis(trichloromethyl)-s-triazine,2,4-bis(trichloromethyl)-6-styryl-s-triazine,2-(naphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine,2-(4-methoxynaphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine,2,4-trichloromethyl-(piperonyl)-6-triazine,2,4-trichloromethyl(4′-methoxystyryl)-6-triazine, etc.; a borate-basedphoto-polymerization initiator; a carbazole-based photo-polymerizationinitiator; an imidazole-based photo-polymerization initiator; etc.

These photo-polymerization initiators can be employed at a ratio rangingfrom 5 to 200 parts by weight, more preferably 10 to 150 parts by weightbased on 100 parts by weight of the pigments in the color composition.

The aforementioned photo-polymerization initiators can be employedeither singly or as a mixture of two or more kinds thereof. Further,these photo-polymerization initiators can be employed in combinationwith a sensitizer, examples of which including α-acyloxy ester,acylphosphine oxide, methylphenyl glyoxylate, benzyl, 9,10-phenanthrenequinone, camphor quinine, ethylanthraquinone, 4,4′-diethylisophthalophenone, 3,3′,4,4′-tetra(t-butyl peroxycarbonyl)benzophenone,etc.

These sensitizers can be employed at a ratio ranging from 0.1 to 60parts by weight based on 100 parts by weight of the photo-polymerizationinitiator.

The color composition may further comprise a polyfunctional thiol whichis capable of acting as a chain-transfer agent. As for thispolyfunctional thiol, it is possible to employ a compound having two ormore thiol groups. Specific examples of such a compound include hexanedithiol, decane dithiol, 1,4-butanediol bisthiopropionate,1,4-butanediol bisthioglycolate, ethyleneglycol bisthioglycolate,ethyleneglycol bisthiopropionate, trimethylolpropane tristhioglycolate,trimethylolpropane tristhiopropionate, trimethylolpropanetris(3-mercaptobutylate), pentaerythritol tetrakisthioglycolate,pentaerythritol tetrakisthiopropionate, trimercaptopropionatetris(2-hydroxyethyl)isocyanulate, 1,4-dimethylmercaptobenzene,2,4,6-trimercapto-s-triazine,2-(N,N-dibutylamino)-4,6-dimercapto-s-triazine, etc. Thesepolyfunctional thiols can be employed singly or in combination of two ormore kinds.

The mixing ratio of these polyfunctional thiols should preferably beconfined within the range of 0.2 to 150 parts by weight, more preferably0.2 to 100 parts by weight based on 100 parts by weight of the pigmentsin the color composition.

The color composition may further contain a solvent for enabling thepigments to be sufficiently dispersed in the pigment carrier and forenabling the color composition to be coated on the surface of atransparent substrate such as a glass substrate, thereby making itpossible to easily create a layer of a filter segment having a hardenedfilm thickness of 0.2-5 μm. Specific examples of such a solvent include,for example, cyclohexanone, ethyl Cellosolve acetate, butyl Cellosolveacetate, 1-methoxy-2-propyl acetate, diethyleneglycol dimethyl ether,ethyl benzene, ethyleneglycol diethyl ether, xylene, ethyl Cellosolve,methyl-n amyl ketone, propyleneglycol monomethyl ether, toluene,methylethyl ketone, ethyl acetate, methanol, ethanol, isopropyl alcohol,butanol, isobutyl ketone, petroleum solvent, etc. These solvents may beemployed singly or in combination of two or more kinds.

The mixing ratio of these solvents should preferably be confined withinthe range of 800 to 4000 parts by weight, more preferably 1000 to 2500parts by weight based on 100 parts by weight of the pigments in thecolor composition.

The color composition can be manufactured by finely dispersing one ormore kinds of pigments, if required, together with the aforementionedphoto-polymerization initiator in a pigment carrier as well as in anorganic solvent. As for the means for carrying out the dispersion inthis case, it is possible to employ a triple roll mill, a twin-rollmill, a sand mill, a kneader, an attritor, etc. Further, in the case ofa color composition containing two or more kinds of pigments, each ofthe pigments may be separately finely dispersed in a pigment carrier aswell as in an organic solvent to obtain a dispersion, which is thenmixed with other dispersion(s) prepared in the same manner as describedabove.

On the occasion of dispersing pigments in a pigment carrier as well asin an organic solvent, a dispersing agent such as a resin type pigmentdispersing agent, a surfactant, a pigment derivative, etc. can beoptionally employed.

Since this dispersing agent is excellent in enhancing the dispersibilityof pigments and in its effects in preventing the re-flocculation ofpigments after the dispersion thereof, the employment of a colorcomposition in which the pigments are dispersed in a pigment carrier andan organic solvent by making use of this dispersing agent isadvantageous in obtaining a color filter with color display pixelsexcellent in transparency. The mixing ratio of the dispersing agentshould preferably be confined within the range of 0.1 to 40 parts byweight, more preferably 0.1 to 30 parts by weight based on 100 parts byweight of the pigments in the color composition.

The resin type pigment dispersing agent is formed of a compound havingnot only a pigment affinity moiety exhibiting pigment-adsorbingproperties, but also another moiety exhibiting compatibility with apigment carrier, thereby enabling the dispersing agent to adsorb ontothe pigment and to stabilize the dispersion of the pigment in thepigment carrier.

As for specific examples of the resin type pigment dispersing agent,they include polyurethane, polycarboxylate such as polyacrylate,unsaturated polyamide, polycarboxylic acid, (partial) aminepolycarboxylate, ammonium polycarboxylate, alkyl amine polycarboxylate,polysiloxane, long chain polyaminoamide phosphate, hydroxylgroup-containing polycarboxylate and modified compounds thereof, an oilydispersing agent such as amide to be formed through a reaction betweenpoly(lower alkyl imine) and polyester having a free carboxyl group andsalts of the amide, (metha)acrylic acid-styrene copolymer,(metha)acrylic acid-(metha)acrylate copolymer, styrene-maleic acidcopolymer, polyvinyl alcohol, water-soluble resin or water-solublemacromolecular compound such as poly(vinyl pyrrolidone), polyestercompounds, modified polyacrylate compounds, ethylene oxide/propyleneoxide adduct, phosphate, etc. These compounds may be employedindividually or in combination of two or more kinds.

As for this surfactant, it is possible to employ an anionic surfactantsuch as polyoxyethylene alkylether sulfate, dodecylbenzene sodiumsulfonate, alkali salts of styrene-acrylic acid copolymer,alkylnaphthaline sodium sulfonate, alkyldiphenyl ether sodiumdisulfonate, monoethanol amine lauryl sulfate, triethanol amine laurylsulfate, ammonium lauryl sulfate, monoethanol amine stearate, sodiumstearate, sodium lauryl sulfate, monoethanol amine of styrene-acrylicacid copolymer, polyoxyethylene alkylether phosphate, etc.; a nonionicsurfactant such as polyoxyethylene oleyl ether, polyoxyethylene laurylether, polyoxyethylene nonylphenyl ether, polyoxyethylene alkyletherphosphate, polyoxyethylene sorbitan monostearate, polyethyleneglycolmonolaurate, etc.; cationic surfactant such as alkyl quaternary ammoniumsalt and an ethylene oxide adduct thereof, etc.; and an amphotericsurfactant such as an alkyl betaine such as betaine alkyldimethylaminoacetate, alkylimidazoline, etc. These surfactants can be employedsingly or in combination of two or more kinds.

The pigment derivative is formed of a compound comprising an organicpigment having a substituent group introduced therein and shouldpreferably be selected from those whose hue is close to the hue of thepigment to be used. However, when the mixing ratio of pigmentderivatives is relatively small, they may be selected from those whosehue differs from the hue of the pigment to be used.

The organic pigment herein includes aromatic polycyclic compoundsexhibiting a light yellow color, such as naphthalene-based compounds andanthraquinone-based compounds, which are generally not called pigments.As for specific examples of the pigment derivatives, it is possible toemploy those described in JP-A 63-305173 (KOKAI), JP Patent Publication57-15620, JP Patent Publication 59-40172, JP Patent Publication 63-17102and JP Patent Publication 5(1993)-9469. Especially, since pigmentderivatives having a basic group are highly effective in the dispersionof pigment, they can be preferably employed. These pigment derivativesmay be employed singly or in combination of two or more kinds.

The color composition may further contain a storage stabilizing agentfor stabilizing the change of viscosity of the composition in time. Asfor specific examples of the storage stabilizing agent, they include,for example, quaternary ammonium chlorides such as benzyltrimethylchloride, diethylhydroxy amine, etc.; organic acids such as lactic acid,oxalic acid, etc. and methyl ethers thereof; t-butyl pyrocatechol;organic phosphine such as tetraethyl phosphine, tetraphenyl phosphine,etc.; phosphite; etc. The storage stabilizing agent can be employed at aratio of 0.1-10 parts by weight based on 100 parts by weight of thepigment in a color composition.

The color composition may further contain an adherence improver, such asa silane coupling agent, for the purpose of enhancing the adhesion to asubstrate.

As for specific examples of the silane coupling agent, they includevinyl silanes such as vinyl tris(β-methoxyethoxy)silane, vinylethoxysilane, vinyltrimethoxy silane, etc.; (metha)acrylsilanes such asγ-methacryloxypropyl silane, etc.; epoxy silanes such asβ-(3,4-epoxycyclohexyl)ethyltrimethoxy silane,β-(3,4-epoxycyclohexyl)methyltrimethoxy silane,β-(3,4-epoxycyclohexyl)ethyltriethoxy silane,β-(3,4-epoxycyclohexyl)methyltriethoxy silane, γ-glycidoxypropyltrimethoxy silane, γ-glycidoxypropyl triethoxy silane, etc.; aminosilanes such as N-β(aminoethyl) γ-aminopropyl trimethoxy silane,N-β(aminoethyl) γ-aminopropyl triethoxy silane, N-β(aminoethyl)γ-aminopropyl methyldiethoxy silane, γ-aminopropyl triethoxy silane,γ-aminopropyl trimethoxy silane, N-phenyl-γ-aminopropyl trimethoxysilane, N-phenyl-γ-aminopropyl triethoxy silane, etc.; and thiosilanessuch as γ-mercaptopropyl trimethoxy silane, γ-mercaptopropyl triethoxysilane, etc. These silane coupling agents can be employed at a ratio of0.01-100 parts by weight based on 100 parts by weight of the pigment ina color composition.

The color composition can be formulated as a gravure offset printingink, a waterless offset printing ink, a silk screen printing ink, or asolvent developing type or alkaline developing type color resist. Thecolor resist is formulated such that the pigment(s) is dispersed in acomposition comprising a thermoplastic resin, thermosetting resin orphotosensitive resin, a monomer, a photo-polymerization initiator and anorganic solvent.

The pigment should preferably be incorporated at a ratio of 5-70% byweight based on the quantity (100% by weight) of solids of the colorcomposition. More preferably, the pigment should be incorporated at aratio of 20-50% by weight, the balance being substantially constitutedby a resinous binder that can be provided by a pigment carrier.

The color composition should preferably be formulated such that bulkyparticles 5 μm or more in size, preferably, bulky particles 1 μm or morein size, more preferably, bulky particles 0.5 μm or more in size as wellas particles intermingled therein are completely removed from thecomposition by making use of any suitable means such as centrifugalseparation, sintered filter, membrane filter, etc.

The color filter according to one embodiment of the present invention isprovided, on a transparent substrate, with a red pixel, a green pixeland a blue pixel, all of which can be formed by means of printing orphotolithography using each of the aforementioned color compositions.

As for the transparent substrate, it is possible to employ a glass platemade of a material such as a soda-lime glass, low alkali borosilicateglass, alkaliless almino borosilicate glass, etc; and a resin plate madeof a material such as polycarbonate, poly(methyl methacrylate),polyethylene terephthalate, etc. For the purpose of driving the liquidcrystal after the fabrication of a liquid crystal panel, a transparentelectrode consisting of a combination of metal oxides such as indiumoxide, tin oxide, zinc oxide, antimony oxide may be formed on thesurface of the glass plate or resin plate.

Since the patterning of these color segments by means of printing can beperformed by simply repeating the printing and drying of a colorcomposition that has been prepared as various kinds of printing inks,the printing method is advantageous as a manufacturing method of a colorfilter in terms of manufacturing cost and mass production. Further, dueto the recent developments in printing techniques, it is now possible toperform the printing of a very fine pattern which is excellent indimensional precision as well as smoothness. In order to perform theprinting, the ink should preferably be formulated such that it cannot bedried or solidified on the surface of a printing plate or blanket.Furthermore, it is also important to control the fluidity of ink on thesurface of the printing machine, so that it may be advisable to adjustthe ink viscosity by making use of a dispersant or an extender pigment.

The inkjet method is a method wherein an inkjet apparatus having aplurality of small injection ports (inkjet head) are arrayed for eachcolor is employed, and the printing is directly performed on atransparent substrate or a substrate having an active element, such as aTFT formed thereon.

When each of the colored pixels is to be formed by means ofphotolithography, a color composition which has been formulated as asolvent developing type or alkaline developing type color resist iscoated on the surface of the transparent substrate by any desired methodof coating, such as spray coating, spin coating, slit coating, rollcoating, etc., thereby forming a layer having a thickness (as dried) of0.2-10 μm.

On the occasion of drying the coated layer, it may be performed bymaking use of a vacuum dryer, convection oven, IR oven, hot plate, etc.The layer thus dried as required is then subjected to the exposure toultraviolet rays through a mask having a predetermined pattern anddisposed in or out of contact with this layer.

Subsequently, the resultant layer is dipped in a solvent or an alkalinedeveloping solution or sprayed with a developing solution by means of aspraying machine, thereby removing the uncured portion, to obtain adesired pattern. Thereafter, the same procedures are repeated for othercolors, thus manufacturing a color filter.

Further, for the purpose of promoting the polymerization of the colorresist, heating may be applied to the coated resist. According to thisphotolithography method, it is possible to manufacture a color filterwhich is further excellent in precision as compared with that obtainedfrom the aforementioned printing methods.

On the occasion of performing the development, an aqueous solution suchas sodium carbonate, sodium hydroxide, etc. can be employed as analkaline developing solution. It is also possible to employ an organicalkali such as dimethylbenzyl amine, triethanol amine, etc. Further, thedeveloping solution may contain a defoaming agent or a surfactant. Asfor the developing treatment, it is possible to employ a showerdeveloping method, a spray developing method, a dip developing method, apaddle developing method, etc.

Incidentally, in order to enhance the sensitivity to ultravioletexposure, a water-soluble or alkali-soluble resin such as, for example,polyvinyl alcohol or a water-soluble acrylic resin may be coated on thecolor resist that has been coated and dried in advance, thereby forminga film which is capable of minimizing the effects of oxygen to obstructthe polymerization. Thereafter, the color resist is subjected toultraviolet exposure.

The color filter according to the present invention can be manufacturedby means of an electrodeposition method, a transfer method or inkjetmethod other than the aforementioned methods. The electrodepositionmethod is a method which is featured in that, by taking advantage of atransparent conductive film formed on the surface of a transparentsubstrate, each of the color filter segments is electrodeposited on thetransparent conductive film through the effects of electrophoresis ofcolloidal particles, thereby manufacturing the color filter.

On the other hand, the transfer method is a method which is featured inthat a color filter layer is formed in advance on the surface of areleasable transfer base sheet and then this color filter layer istransferred onto a desired transparent substrate.

Next, a liquid crystal display device which is equipped with the colorfilter of the present invention will be explained.

FIG. 2 is a cross-sectional view schematically illustrating the liquidcrystal display device which is provided with the color filter of thepresent invention. The liquid crystal display device 4 shown in FIG. 2illustrates a typical example of a TFT drive type liquid crystal displaydevice for use in a notebook-sized personal computer. This liquidcrystal display device 4 is provided with a pair of transparentsubstrates 5 and 6, which are arranged face to face with a gapinterposed therebetween. The gap between them is filled with a liquidcrystal (LC).

This LC is aligned depending on the kind of driving mode, such as TN(Twisted Nematic), STN (Super Twisted Nematic), IPS (In-Planeswitching), VA (Vertical Alignment), OCB (Optically CompensatedBirefringence), etc.

On the inner wall of the first transparent substrate 5, there is formeda TFT (thin film transistor) array 7. On this TFT array 7 is deposited atransparent electrode layer 8 formed of ITO, for example. On thistransparent electrode layer 8 is further provided an alignment layer 9.Further, a polarizer (polarizing plate) 10, comprising an opticalretardation film, is formed on the outer surface of the transparentsubstrate 5.

On the other hand, on the inner wall of the second transparent substrate6, there is formed a color filter 11 according to one embodiment of thepresent invention. The red, green and blue filter segments constitutingthe color filter 11 are separated from each other by a black matrix (notshown). If required, a transparent protective film (not shown) may beformed so as to cover the color filter 11. Furthermore, a transparentelectrode layer 12, formed of ITO for example, is formed on thisprotective film. An alignment layer 13 is deposited so as to cover thetransparent electrode layer 12. Further, a polarizer 14 is formed on theouter surface of the transparent substrate 6. Incidentally, a backlightunit 16 equipped with a triple wavelength lamp 15 is disposed below thepolarizer 10.

As explained above, even if there is a possibility that the values ofperpendicular optical retardation of red, green and blue colored pixelsconstituting the color filter may be brought into a discontinuous statedue to the specific selection of pigments to be used or due to thepulverization of pigments in an attempt to obtain a color filter offurther enhanced contrast, since there is employed aretardation-regulating agent having at least one planar structure groupand a photopolymerizable group or a thermally polymerizable group on atleast two different portions of the planar structure group, it is nowpossible to provide a coloring composition for a color filter that iscapable of regulating the values of perpendicular optical retardation totake optimum values so as to make them continuous.

Furthermore, when such a coloring composition for a color filter isemployed for the manufacture of a color filter, it is possible to obtaina color filter having a continuous state satisfying the conditions of:Rth(R)≧Rth(G)≧Rth(B) or Rth(R)≦Rth(G)≦Rth(B).

When a liquid crystal display device is manufactured by making use ofsuch a color filter so as to satisfy the optical characteristics of theoptical compensation layer and other constituent members, especially tosatisfy the wavelength dispersing characteristics of retardation, it ispossible to prevent the generation of non-uniformity of the polarizedstate of light passing through the display region of each colored pixel,thus making it possible to obtain a liquid display device which isexcellent in oblique viewing angle display. Further, since the blackcolor display is compensated in oblique viewing angle, it is possible toreproduce a black color which is minimized in color shifting andexcellent in neutrality, thus exhibiting highly excellent displaycharacteristics.

As explained above, according to the present invention, since it ispossible to regulate the retardation, which is specific to each colorfilter, it is possible to minimize the difference in perpendicularoptical retardation of each color even though the color filter that canbe obtained is of a high quality exhibiting a contrast value of not lessthan 1000 or not less than 3000.

Furthermore, since the kinds of pigments to be employed are specificallyselected and dispersed in a transparent resin, it is now possible tofurther enhance the axial visibility.

When a liquid crystal display device is manufactured by making use ofsuch a color filter, it is possible to minimize the non-uniformity ofthe polarized state of light passing through the display region of eachcolored pixel, thus making it possible to obtain a liquid display devicewhich is excellent not only in oblique visibility but also in axialvisibility.

EXAMPLES

Although specific examples of the present invention will be explainedbelow, it should not be construed that the present invention is limitedto these examples. Further, as the materials to be employed in theseexamples are very sensitive to light, it is required to prevent thesensitization of the materials by redundant light such as natural lightby performing all necessary tasks under yellow or red light.

Incidentally, “part(s)” in the following examples and comparativeexamples means “weight part(s)”. Further, the symbols of pigments areindicated by a color index number. For example, “PR254” means “C.I.Pigment Red 254”, and “PY150” means “C.I. Pigment Yellow 150”.

The following Table 1 illustrates the pigment derivatives employed inthe following examples.

TABLE 1 Pigment derivatives Chemical structure D-1

D-2

D-3

D-4

a) Manufacture Of Refined Pigment

A refined pigment to be used in Examples and Comparative Examples wasmanufactured according to the following methods. Then, the primaryparticle diameter d50 of pigments thus obtained was calculated by takingthe pictures of the pigments in the view by making use of a transmissionelectron microscope JEM-2010 (manufactured by Japan Electron Co., Ltd.)and by performing the image analysis of the pictures. The primaryparticle diameter d50 herein represents a particle diameter (a diameterof equivalent circle) which corresponds to a particle diameter asmeasured where an integrated quantity in the cumulative curve of numberparticle size distribution is 50% of the total quantity. The cumulativecurve of number particle size distribution is obtained by plotting themean value of the major axis and minor axis of 100 primary particles ofeach pigment, constituting the aggregate on the two-dimentional image,with respect to the number of the particles.

Manufacturing Example 1

100 parts (based on weight, the same hereinafter) of adiketopyrrolopyrrol-based red pigment PR254 (Ciba Speciality ChemicalsCo., Ltd. “IRGAPHOR RED B-CF”; R-1), 18 parts of a dye derivative (D-2),1000 parts of pulverized sodium chloride, and 120 parts of diethyleneglycol were put into a 1 gallon stainless steel kneader (InoueSeisakusho Co., Ltd.) and kneaded for 10 hours at a temperature of 60°C.

Then, the resultant mixture was introduced into 2000 parts of hot waterand stirred for about one hour by means of a high-speed mixer whileheating it at a temperature of about 80° C. to obtain a slurry product.This slurry product was then subjected to repeated filtration and waterwashing to remove sodium chloride, and the solvent was dried for 24hours at a temperature of 80° C. to obtain 115 parts of a saltmilling-treated pigment (Red-2). The primary particle diameter of thepigment thus obtained is shown in the following Table 2.

Manufacturing Example 2

100 parts (based on weight, the same hereinafter) of anthraquinone-basedred pigment PR177 (Ciba Speciality Chemicals Co., Ltd. “CROMOPHTAL REDA2B), 8 parts of a dye derivative (D-2), 700 parts of pulverized sodiumchloride, and 180 parts of diethylene glycol were put into a 1 gallonstainless steel kneader (Inoue Seisakusho Co., Ltd.) and kneaded for 4hours at a temperature of 70° C. Then, the resultant mixture wasintroduced into 4000 parts of hot water and stirred for about one hourby means of a high-speed mixer while heating it at a temperature ofabout 80° C. to obtain a slurry product. This slurry product was thensubjected to repeated filtration and water washing to remove sodiumchloride, and the solvent was dried for 24 hours at a temperature of 80°C. to obtain 102 parts of a salt milling-treated pigment (Red-3). Theprimary particle diameter of the pigment thus obtained is shown in thefollowing Table 2.

Manufacturing Example 3

170 parts of tert-amyl alcohol was poured into a sulfonated flask in anitrogen atmosphere and then 11.04 parts of sodium was added to thetert-amyl alcohol to obtain a mixture which was then heated at atemperature of 92-102° C. to melt the sodium. While vigorously stirringthe molten sodium, the mixture was kept overnight at a temperature of100-107° C. Then, a solution containing 44.2 parts of4-chlorobenzonitrile and 37.2 parts of diisopropyl succinate, which weredissolved in advance at 80° C. in 50 parts of tert-amyl alcohol, wasslowly added to the aforementioned mixture over two hours at atemperature of 80-98° C. Then, the resultant reaction mixture wasfurther stirred for three hours at 80° C., and concurrently 4.88 partsof diisopropyl succinate was added dropwise to the reaction mixture.This reaction mixture was cooled to room temperature and then 270 partsof methanol, 200 parts of water and 48.1 parts of concentrated sulfuricacid were added to this reaction mixture at a temperature of 20° C.Then, the resultant mixture was stirred for 6 hours at a temperature of20° C. The resultant red mixture was subjected to filtration and thenwashed with methanol and water and allowed dry to obtain 46.7 parts ofred pigment (R-4). The primary particle diameter of the pigment thusobtained is shown in the following Table 2.

Manufacturing Example 4

120 parts of copper phthalocyanine halide-based green pigment PG36 (ToyoInk Manufacturing Co., Ltd. “LIONOL GREEN 6YK”), 1600 parts ofpulverized sodium chloride, and 270 parts of diethylene glycol were putinto a 1 gallon stainless steel kneader (Inoue Seisakusho Co., Ltd.) andkneaded for 12 hours at a temperature of 70° C. Then, the resultantmixture was introduced into 5000 parts of hot water and stirred forabout one hour by means of a high-speed mixer while heating it at atemperature of about 70° C. to obtain a slurry product. This slurryproduct was then subjected to repeated filtration and water washing toremove sodium chloride, and the solvent was dried for 24 hours at atemperature of 80° C. to obtain 117 parts of a salt milling-treatedpigment (G-1). The primary particle diameter of the pigment thusobtained is shown in the following Table 2.

Manufacturing Example 5

46 parts of zinc phthalocyanine was dissolved in a molten saltconsisting of 356 parts of aluminum chloride and 6 parts of sodiumchloride and heated to a temperature of 200° C. Then, the resultantsolution was cooled down to 130° C. and stirred for one hour.Thereafter, the reaction temperature was raised up to 180° C. andbromine was added drop-wise at a rate of 10 parts per hour to thisreaction mixture over 10 hours. Then, chlorine was added drop-wise at arate of 0.8 parts per hour to this reaction mixture over 5 hours. Theresultant reaction mixture was gradually poured into 3200 parts of waterand then subjected to filtration and water washing to obtain 107.8 partsof crude zinc phthalocyanine halide pigment.

The average number of bromine atoms included in one molecule of thiscrude zinc phthalocyanine halide pigment was 14.1 and the average numberof chlorine atoms included in one molecule of this crude zincphthalocyanine halide pigment was 1.9. Then, 120 parts of this crudezinc phthalocyanine halide pigment, 1600 parts of pulverized sodiumchloride, and 270 parts of diethylene glycol were put into a 1 gallonstainless steel kneader (Inoue Seisakusho Co., Ltd.) and kneaded for 12hours at a temperature of 70° C. Then, the resultant mixture was pouredinto 5000 parts of hot water and stirred for about one hour by means ofa high-speed mixer while heating it at a temperature of about 70° C. toobtain a slurry product. This slurry product was then subjected torepeated filtration and water washing to remove sodium chloride and thesolvent was dried for 24 hours at a temperature of 80° C. to obtain 117parts of a salt milling-treated pigment (G-2). The primary particlediameter of the pigment thus obtained is shown in the following Table 2.

Manufacturing Example 6

150 parts of water was poured into a separation flask and then 63 partsof 35% hydrochloric acid was added with stirring to the water to obtaina solution of hydrochloric acid. Then, while taking care of foamingreaction, 38.7 parts of benzene sulfonyl hydrazide was added to thesolution and ice was added to the solution until the temperature ofsolution was cooled down to 0. After this cooling, 19 parts of sodiumnitrite was added to the solution and stirred for 30 minutes at atemperature ranging from 0 to 15° C. Subsequently, sulfamic acid wascontinuously added to the solution until the coloration of potassiumiodide-starch paper could not be recognized any longer.

Furthermore, 25.6 parts of barbituric acid was added to the solution andthen the temperature of the resultant solution was raised up to 55° C.and then stirred for 2 hours. Additionally, 25.6 parts of barbituricacid was added to the solution and then the temperature of the resultantsolution was raised up to 80° C. and sodium hydroxide was continuouslyadded to the solution until the pH thereof became 5. The resultantsolution was stirred for 3 hours at a temperature of 80° C. and then thetemperature of the solution was allowed drop to 70° C. Then, thesolution was subjected to filtration and washing with hot water. Thepress cake thus obtained was dissolved in 1200 parts of hot water toobtain a slurry matter, which was then stirred for two hours at atemperature of 80° C. Subsequently, while keeping this temperature, theslurry matter was subjected to filtration and to hot water washing bymaking use of 2000 parts of hot water heated to 80° C. As a result, itwas possible to confirm that benzene sulfonamide was shifted to thefiltrate.

The press cake thus obtained was dried at a temperature of 80° C. toobtain 61.0, parts of disodium salt of azobarbituric acid. Then, 200parts of water was poured into a separation flask and then 8.1 parts ofdisodium azobarbiturate powder was added with stirring to the water anddispersed therein. The solution having disodium azobarbiturate powderhomogeneously dispersed therein was heated up to 95° C. and then 5.7parts of melamine and 1.0 parts of diarylaminomelamine were added to thesolution.

Furthermore, a green color solution, which was obtained by dissolving6.3 parts of cobalt chloride (II) hexahydrate in 30 parts of water, wasadded drop-wise to the aforementioned solution over 30 minutes. Afterfinishing the addition of the green color solution, the complexation wasallowed to take place in the solution for 1.5 hours at a temperature of90° C. Subsequently, the pH of the solution was adjusted to 5.5 and 20.4parts of the emulsified solution composed of 4 parts of xylene, 0.4 partof sodium oleate and 16 parts of water was added to thepreviously-mentioned solution and the resultant solution was stirred for4 hours under heating. The resultant solution was then cooled down to70° C. and immediately subjected to filtration and repeated waterwashing using hot water heated to 70° C. until the inorganic salts werewashed away. Subsequently, the product was subjected to drying andcrushing processes to obtain 14 parts of azo-based yellow pigment (Y-2).The primary particle diameter of the pigment thus obtained is shown inthe following Table 2.

Manufacturing Example 7

100 parts of copper phthalocyanine-based blue pigment PB15:6 (Toyo InkManufacturing Co., Ltd. “LIONOL BLUE ES”), 800 parts of pulverizedsodium chloride, and 100 parts of diethylene glycol were put into a 1gallon stainless steel kneader (Inoue Seisakusho Co., Ltd.) and kneadedfor 12 hours at a temperature of 70° C. Then, the resultant mixture wasintroduced into 3000 parts of hot water and stirred for about one hourby means of a high-speed mixer while heating it at a temperature ofabout 70° C. to obtain a slurry product. This slurry product was thensubjected to repeated filtration and water washing to remove sodiumchloride, and the solvent was dried for 24 hours at a temperature of 80°C. to obtain 98 parts of a salt milling-treated pigment (B-1). Theprimary particle diameter of the pigment thus obtained is shown in thefollowing Table 2.

TABLE 2 Av. primary Colors Symbols particle diameter (nm) RED R-1 68.8R-2 24.8 R-3 28.1 R-4 23.2 GREEN G-1 22.4 G-2 24.3 YELLOW Y-1 99.5 Y-225.2 BLUE B-1 28.3 Y-1: PY150 (Lancces Co., Ltd. “E4GN”)

b) Preparation Of a Solution Of Acrylic Resin

800 parts of cyclohexanone was put into a reaction vessel and heated ata temperature of 100° C. while introducing nitrogen gas into thereaction vessel and then, while maintaining this temperature, a mixturecomprising the following monomers and thermal polymerization initiatorwas added drop-wise to the cyclohexanone over one hour, thereby allowinga polymerization reaction to take place.

Styrene 60.0 parts Methacrylic acid 60.0 parts Methyl methacrylate 65.0parts Butyl methacrylate 65.0 parts Azobis-isobutyronitrile 10.0 parts

After finishing the addition of the aforementioned mixture, the reactionof this mixture was further allowed to take place for 3 hours at atemperature of 100° C. Thereafter, a solution consisting of 2.0 parts ofazobis-isobutyronitrile, which was dissolved in 50 parts ofcyclohexanone, was added to the reaction mixture and the reactionthereof was continued for one hour at a temperature of 100° C. to obtaina resin solution. After being cooled down to room temperature, about 2 gof this resin solution was sampled out and thermally dried for 20minutes at a temperature of 180° C. to measure the amount of nonvolatilematter. A suitable amount of cyclohexanone was added to the resinsolution that had been synthesized in advance so as to make the ratio ofthe nonvolatile matter 20% by weight, thus preparing an acrylic resinsolution.

c) Preparation Of Pigment Dispersion

A mixture having a composition (weight ratio) shown in the followingTable 3 was homogeneously stirred and then, by making use of zirconiabeads having a diameter of 1 mm, the dispersion of the components of thecomposition was performed for 5 hours by means of a sand mill, and theresultant product was subjected to filtration by making use of a 5 μmfilter to obtain a pigment dispersion of each color.

TABLE 3 Pigment dispersions RP-1 RP-2 RP-3 GP-1 GP-2 BP-1 Pigments 1stpigment R-1 R-2 R-4 G-1 G-1 B-1 2nd pigment R-3 R-3 R-3 Y-1 Y-2 —Pigment derivative D-1 D-1 D-1 D-3 D-3 D-4 Composition 1st pigment 9.69.6 9.6 8.3 8.3 9.6 2nd pigment 1.1 1.1 1.1 5.4 5.4 0.4 3rd pigment — —— 0.0 0.0 0.0 Pigment 1.3 1.3 1.3 1.8 1.8 2.0 derivative Acrylic 40.040.0 40.0 36.5 36.5 40.0 resin solution Organic solvent 48.0 48.0 48.048.0 48.0 48.0 Total 100.0 100.0 100.0 100.0 100.0 100.0

Monomer: trimethyrolpropane triacrylate (NK Ester ATMPT; Shin-NakamuraKagaku Co., Ltd.)

Photopolymerization-initiator:2-methyl-1-[4-(methylthio)phenyl]-2-morphorinopropane-1-one (Irgar Cure907; Ciba Speciality Chemicals Co., Ltd.)

Sensitizer: 4,4′-bis(diethylamino)benzophenone (EAB-F; HodogayaChemicals Co.)

Organic solvent: cyclohexanone

d) Retardation Regulating Agent

The following commonly available compounds available were employed asretardation regulating agents.

Melamine compound Nippon Carbide Industries Co. (product name: NIKALACMX-750) Porphyrin compound Tokyo Kasei Industries Co. (product name:TETRAPHENYL PORPHYRIN) Epoxy compound Japan Epoxy Resin Co. (productname: Epicoat 828)

e) Preparation Of Coloring Composition (Hereinafter Referred to as ColorResist)

A mixture having a composition (weight ratio) shown in the followingTable 4 was homogeneously stirred and then subjected to filtration bymaking use of a 1 μm filter, thereby obtaining resists of variouscolors.

TABLE 4 Resist RR-1 RR-2 RR-3 RR-4 RR-5 GR-1 GR-2 Pigment dispersionRP-1 RP-1 RP-2 RP-3 RP-3 GP-1 GP-1 Retardation-regulating agent —Melamine — — Porphrin — Melamine 12.0 12.0 8.0 Composition Pigmentdispersion 36.0 36.0 36.0 36.0 36.0 45.0 45.0 Acrylic resin 12.0 — 12.012.0 — 8.0 — solution Monomer 4.0 4.0 4.0 4.0 4.0 4.8 4.8 Photopolymerization 3.4 3.4 3.4 3.4 3.4 2.8 2.8 initiator Sensitizer 0.4 0.40.4 0.4 0.4 0.2 0.2 Organic solvent 44.2 44.2 44.2 44.2 44.2 39.2 39.2Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Resist GR-3 GR-4 GR-5GR-6 GR-7 BR-1 BR-2 Pigment dispersion GP-1 GP-2 GP-2 GP-2 GP-2 BP-1BP-1 Retardation-regulating agent Polymeric LC — Melamine Epoxy Porphrin— Melamine 8.0 8.0 8.0 8.0 10.0 Composition Pigment dispersion 45.0 45.045.0 45.0 45.0 32.0 32.0 Acrylic resin — 8.0 — — — 10.0 — solutionMonomer 4.8 4.8 4.8 4.8 4.8 5.6 5.6 Photo polymerization 2.8 2.8 2.8 2.82.8 2.0 2.0 initiator Sensitizer 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Organicsolvent 39.2 39.2 39.2 39.2 39.2 50.2 50.2 Total 100.0 100.0 100.0 100.0100.0 100.0 100.0

f) Manufacture Of the Coated Films Of Various Colors

By means of spin coating, each of the color resists shown in above Table4 was coated on the surface of a glass substrate and then pre-baked for20 minutes in a clean oven at a temperature of 70° C. Then, after beingcooled to room temperature, the substrate was exposed to ultravioletrays by making use of an ultra-high pressure mercury lamp. Thereafter,the resultant substrate was subjected to spray development by making useof an aqueous solution of sodium carbonate heated up to 23° C., afterwhich the resultant substrate was washed with ion-exchange water andair-dried. Subsequently, the resultant substrate was post-baked for 30minutes in a clean oven at a temperature of 230° C., thereby forming acolored coated film of each color. The film thickness of the driedcoated film was 2.0 μm in all cases.

g) Measurements Of Chromaticity Of Colored Coated Film, SpectralTransmittance, Perpendicular Optical Retardation, and Contrast

(Chromaticity and Spectral Transmittance)

The chromaticity in a chromaticity diagram for an XYZ colorspecification system was measured by making use of a spectrophotometer(“OSP-200”; Olympus Co., Ltd.). The chromaticity values of each of thecolored coated films which were manufactured by making use of each ofthe color resists shown in above Table 4 are shown in the followingTable 7.

(Value Rth of Perpendicular Optical Retardation)

The values of perpendicular optical retardation were determined asfollows. Namely, by making use of a spectroellipsometer (M-220 (tradename); Nippon Bunko Co., Ltd.), the coated film was measured from thedirection which was angled at 45° from the normal direction of thesubstrate having a coated film formed thereon at intervals in wavelengthof 5 nm in the range of 400 nm to 700 nm to obtain an ellipsoparameterδ. By making use of equation Δ=δ/360×λ, the value of optical retardationΔ(λ) was calculated. Then, by making use of this value, thethree-dimensional refractive index was calculated and the value Rth ofperpendicular optical retardation was calculated from the followingequation. In this case, a wavelength of 610 nm was used for the redcolored pixel, a wavelength of 550 nm was used for the green coloredpixel, and a wavelength of 450 nm was used for the blue colored pixel.

Rth={(Nx+Ny)/2−Nz}×d

wherein Nx is a refractive index in the direction of x in the plane ofthe colored pixel; Ny is a refractive index in the direction of y in theplane of the colored pixel; and Nz is a refractive index in thethickness-wise direction of the colored pixel; Nx being defined as alagging axis represented by Nx≧Ny; and d is the thickness (nm) of acolored pixel.

The following Table 5 illustrates the value Rth of perpendicular opticalretardation of each colored coated film manufactured by making use ofeach of the color resists shown in above Table 4.

(Contrast)

A polarizing plate was laminated on the opposite surfaces of thesubstrate having coated films formed thereon and then the luminance oflight (Lp) under the condition where these polarizing plates aredisposed parallel with each other was compared with the luminance oflight (Lc) under the condition where these polarizing plates aredisposed to intersect orthogonally with each other to obtain the ratioof Lp/Lc, thereby calculating the contrast (C).

Then, by making use of a basic substrate having no colored pixel formedthereon, the contrast (CS) was measured, thereby enabling the ratio ofC/CS to be used for the normalization. Incidentally, the luminance wasmeasured by making use of a color luminance meter (“BM-5A”; Topcon Co.,Ltd.) under the condition of a 2° viewing angle. As for the polarizingplate, “NPF-SEG1224DU” (Nitto Denko Co., Ltd.) was employed. Table 5shows the contrast of each of the colored coated films which weremanufactured by making use of each of the color resists shown in Table 4above.

TABLE 5 Resist coating RR-1 RR-2 RR-3 RR-4 RR-5 GR-1 GR-2 CIEchromaticity x 0.652 0.651 0.649 0.649 0.649 0.279 0.278 (C lightsource) y 0.330 0.329 0.328 0.329 0.329 0.601 0.598 Y 19.5 19.7 18.619.6 19.6 53.3 54.9 C/CS 0.31 0.32 0.55 0.96 0.95 0.40 0.41 Contrast2520 2560 7250 9500 9410 4540 4560 Rth −10 10 25 −8 10 −22 6 Resistcoating GR-3 GR-4 GR-5 GR-6 GR-7 BR-1 BR-2 CIE chromaticity x 0.2780.281 0.278 0.278 0.278 0.136 0.136 (C light source) y 0.600 0.600 0.5980.598 0.598 0.103 0.103 Y 54.5 55.3 50.2 50.2 50.2 11.8 11.7 C/CS 0.390.63 0.65 0.63 0.62 0.50 0.51 Contrast 4350 7650 7760 7620 7580 72507320 Rth 2 −21 6 −5 8 4 16

h) Manufacture Of Color Filter

The color filters were manufactured through a combination of colorresists shown in Table 4 above and by the method described below.

Example 1

First of all, by means of spin coating, a red resist (RR-1) was coatedon the surface of a glass substrate having a black matrix formed thereonin advance and then pre-baked for 20 minutes in a clean oven at atemperature of 70° C. Then, after being cooled to room temperature, thesubstrate was exposed, through a photomask, to ultraviolet rays bymaking use of an ultra-high pressure mercury lamp.

Thereafter, the resultant substrate was subjected to spray developmentby making use of an aqueous solution of sodium carbonate heated up to23° C., after which the resultant substrate was washed with ion-exchangewater and air-dried. Further, the resultant substrate was post-baked for30 minutes in a clean oven at a temperature of 230° C., thereby forminga red colored pixel having a stripe-like configuration on the substrate.

Next, by making use of a green resist (GR-3), the green colored pixelwas coated on the surface of the substrate in the same manner asdescribed above and, further, by making use of a blue resist (BR-1), theblue colored pixel was coated on the surface of the substrate in thesame manner as described above, thereby obtaining a color filter. Thefilm thickness of each of these colored pixels was 2.0 μm in all cases.

Example 2

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the green resist was changed to(GR-6) from (GR-3).

Example 3

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-2)from (RR-1) and the green resist was changed to (GR-2) from (GR-3).

Example 4

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-3)from (RR-1) and the green resist was changed to (GR-2) from (GR-3).

Example 5

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-3)from (RR-1) and the green resist was changed to (GR-5) from (GR-3).

Example 6

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-4)from (RR-1).

Example 7

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-5)from (RR-1) and the green resist was changed to (GR-2) from (GR-3).

Example 8

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-4)from (RR-1) and the green resist was changed to (GR-6) from (GR-3).

Example 9

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-5)from (RR-1) and the green resist was changed to (GR-7) from (GR-3).

Example 10

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-4)from (RR-1), the green resist was changed to (GR-7) from (GR-3) and theblue resist was changed to (BR-2) from (BR-1).

Comparative Example 1

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the green resist was changed to(GR-1) from (GR-3).

Comparative Example 1

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the green resist was changed to(GR-1) from (GR-3).

Comparative Example 2

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the green resist was changed to(GR-4) from (GR-3).

Comparative Example 3

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-2)from (RR-1), and the green resist was changed to (GR-1) from (GR-3).

Comparative Example 4

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-2)from (RR-1), and the green resist was changed to (GR-4) from (GR-3).

Comparative Example 5

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-3)from (RR-1), and the green resist was changed to (GR-1) from (GR-3).

Comparative Example 6

A color filter was obtained by repeating the same procedures asdescribed in Example 1 except that the red resist was changed to (RR-3)from (RR-1), and the green resist was changed to (GR-4) from (GR-3).

i) Manufacture Of a Liquid Crystal Display Device

A transparent ITO electrode layer was formed on the color filterobtained as described above and then a polyimide alignment layer wasformed on the ITO electrode layer. Further, a polarizing plate wasformed on the opposite surface of the glass substrate.

On the other hand, a TFT array and pixel electrodes were formed on onesurface of another (second) glass substrate and a polarizing plate wasformed on the opposite surface of this glass substrate. Two glasssubstrates thus prepared were positioned face to face so as to make theelectrode layers thereof face each other. Then, these glass substrateswere aligned with each other while securing a predetermined gap betweenthem by making use of spacer beads, and then the outer circumference ofthis composite body of substrates was entirely sealed while leaving anopening for injecting a liquid crystal composition.

Thereafter, a liquid crystal composition was injected, via the opening,into the gap and then the opening was closed. The polarizing plate wasfurnished with an optical compensation layer which was optimized so asto realize a wide angle view-field display. The liquid crystal displaydevice thus manufactured was assembled with a backlight unit to obtain aliquid crystal panel.

j) Assessment Of Visibility Of Liquid Crystal Display Device On theOccasion Of Displaying Black Color

The liquid crystal display device manufactured as described above wasoperated so as to display a black color and the amount of the lightleaked out from the liquid crystal panel (orthogonally permeated light;leaked light) in the normal direction (front) of the liquid crystalpanel and in a slanted direction which was inclined by 45° from thenormal direction (oblique angle) was visually observed. The assessmentranking was as follows, the results being illustrated in the followingTable 6.

TABLE 6 Visibility at Resist Rth C/CS black display Red Green Blue R G BR G B Front Oblique Ex. 1 RR-1 GR-3 BR-1 −10 2 4 0.31 X 0.39 X 0.50 ◯ X◯ Ex. 2 RR-1 GR-6 BR-1 −10 −5 4 0.31 X 0.62 ◯ 0.50 ◯ Δ ◯ Ex. 3 RR-2 GR-2BR-1 10 6 4 0.32 X 0.41 X 0.50 ◯ X ◯ Ex. 4 RR-3 GR-2 BR-1 25 6 4 0.55 ◯0.41 X 0.50 ◯ Δ ◯ Ex. 5 RR-3 GR-5 BR-1 25 6 4 0.55 ◯ 0.65 ◯ 0.50 ◯ ◯ ◯Ex. 6 RR-4 GR-3 BR-1 −8 2 4 0.96 ◯ 0.39 X 0.50 ◯ Δ ◯ Ex. 7 RR-5 GR-2BR-1 10 6 4 0.95 ◯ 0.41 X 0.50 ◯ Δ ◯ Ex. 8 RR-4 GR-6 BR-1 −8 −5 4 0.96 ◯0.63 ◯ 0.50 ◯ ◯ ◯ Ex. 9 RR-5 GR-7 BR-1 10 8 4 0.95 ◯ 0.62 ◯ 0.50 ◯ ◯ ◯Ex. 10 RR-4 GR-7 BR-2 −8 8 16 0.96 ◯ 0.62 ◯ 0.51 ◯ ◯ ◯ Comp. Ex. 1 RR-1GR-1 BR-1 −10 −22 4 0.31 X 0.40 X 0.50 ◯ X X Comp. Ex. 2 RR-1 GR-4 BR-1−10 −21 4 0.31 X 0.63 ◯ 0.50 ◯ Δ X Comp. Ex. 3 RR-2 GR-1 BR-1 25 −22 40.32 X 0.40 X 0.50 ◯ X X Comp. Ex. 4 RR-2 GR-4 BR-1 25 −21 4 0.32 X 0.63◯ 0.50 ◯ Δ X Comp. Ex. 5 RR-3 GR-1 BR-1 −8 −22 4 0.55 ◯ 0.40 X 0.50 ◯ ΔX Comp. Ex. 6 RR-3 GR-4 BR-1 −8 −21 4 0.55 ◯ 0.63 ◯ 0.50 ◯ ◯ X ◯:Excellent Δ: Good X: Bad

It can be seen from Table 6 above that the color filters obtained inExamples 1 through 9 were employed in a liquid crystal display device,thus proving it is possible to obtain a liquid crystal display devicewhich is excellent in oblique visibility.

Further, in the cases of the color filters of Examples 5, 8 and 9, sinceit was made possible to obtain an enhanced contrast when observed fromthe front of the panel, it was possible to obtain a liquid crystaldisplay device which was excellent in visibility also in the axialdirection of the panel.

Whereas, in the cases of the color filters obtained in ComparativeExamples 1 through 6, since the balance of perpendicular opticalretardation was poor among the red pixel, the green pixel and bluepixel, color shift was caused to generate when observed in the obliquedirection, thus deteriorating the oblique visibility thereof.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A coloring composition for a color filter, which comprises a transparent resin, an organic pigment dispersed in the transparent resin, and a retardation-regulating agent containing a compound which is capable of increasing a retardation.
 2. The coloring composition according to claim 1, wherein the retardation-regulating agent is an organic compound having a planar structure functional group with at least one cross-linking group.
 3. The coloring composition according to claim 2, wherein the organic compound is at least one compound selected from the group consisting of melamine compounds, porphyrin compounds, epoxy compounds and polymeric liquid crystal compounds.
 4. The coloring composition according to claim 1, wherein a contrast C represented from the following equation is not less than 3000, C=Lp/Lc wherein Lp is the luminance of light measured by means of a luminance meter as the light is passed through a laminated structure consisting of a pair of polarizing plates with a coated film of the coloring composition of single color deposited on a transparent substrate being sandwiched therebetween after a backlight is applied to one of the polarizing plates and permitted to emit from the other of the polarizing plates under a condition wherein axes of these polarizing plates are parallel with each other; and Lc is the luminance of light measured under the same conditions as described above except that axes of these polarizing plates are orthogonal to each other.
 5. The coloring composition according to claim 1, wherein a ratio of a contrast C to a contrast CS is not less than 0.45, the contrast C is represented the following equation, C=Lp/Lc wherein Lp is the luminance of light measured by means of a luminance meter as the light is passed through a laminated structure consisting of a pair of polarizing plates with a coated film of the coloring composition of single color deposited on a transparent substrate being sandwiched therebetween after a backlight is applied to one of the polarizing plates and permitted to emit from the other of the polarizing plates under a condition wherein axes of these polarizing plates are parallel with each other; and Lc is the luminance of light measured under the same conditions as described above except that axes of these polarizing plates are orthogonal to each other, and the contrast CS is a value measured under the same conditions as described above except that the transparent substrate without the coated film of the coloring composition is sandwiched between said pair of polarizing plates.
 6. The coloring composition according to claim 1, wherein the organic pigment is selected from those having an average primary particle diameter ranging from 5 to 40 nm.
 7. A color filter comprising a transparent substrate, and colored pixels of at least one color which is formed on the transparent substrate, wherein the colored pixels are formed using a coloring composition including a transparent resin, an organic pigment dispersed in the transparent resin, and a retardation-regulating agent containing a compound which is capable of increasing a retardation.
 8. The color filter according to claim 7, wherein the colored pixel is formed of a green pixel.
 9. The color filter according to claim 7, wherein the colored pixel is formed of a green pixel and red pixel.
 10. A liquid crystal display device comprising: a first transparent substrate having a thin film transistor array and a first transparent electrode formed thereon; a second transparent substrate disposed to face the first transparent substrate and having a color filter and a second transparent electrode formed thereon; and a liquid crystal layer interposed between the first transparent substrate and the second transparent substrate; wherein the color filter is provided with colored pixels of at least one color which are formed on the second transparent substrate by using a coloring composition including a transparent resin, an organic pigment dispersed in the transparent resin, and a retardation-regulating agent containing a compound which is capable of increasing a retardation. 